House Rules

Characters
Average Hit Points
Elves
Gnomes
Half-Orcs
Bards
Clerics
Druids
Sorcerers
Wizards
Spontaneous Casting
Specialist Bonus

Skills and Feats
Concentration Skill
Craft (Alchemy) Skill
Intimidate Skill
Sneak Skill
Spellcraft Skill
Use Magic Device Skill
Toughness Feat
Item Creation Feats

Combat
Reach Weapons
Halfspear / Shortspear
Heavy Crossbow
Flanking I
Flanking II
Firing into Melee
Death and Dying
Natural 1 or 20
Two Natural 20's

Magic
Detecting Alignments
Non-Auto. Remedies
Returning from Death
The Identify Spell
Scrying

Miscellaneous
Masterwork Items
Falling Damage
Hero Points

Characters

Average Hit Points Option
Any player may, at his option, choose to take an average roll (rounded up) rather than rolling the dice when figuring hit points gained at a new level.  Thus, a player may substitute a "3" for a d4 roll, a "4" for a d6 roll, a "5" for a d8 roll, a "6" for a d10 roll, and a "7" for a d12 roll.

Elves
Elves are not currently a player race.  Instead of four bonus weapon proficiencies, elves now get "Weapon Familiarity: Elves may treat longswords, rapiers, longbows (including composite longbows), and shortbows including composite shortbows) as simple weapons rather than martial weapons."
Credit: Sean K. Reynolds

Gnomes
Gnomes treat bard or illusionist as their favored class, whichever is more advantageous.
Credit: Sean K. Reynolds

Half-Orcs
Half-orcs do not have a Charisma penalty. Half-orcs get a -1 penalty to Diplomacy, Gather Information, and Handle Animal checks.
Credit: Sean K. Reynolds

Bards
Bards can swap out one spell each time they gain a bard level.  Inspire Competence can be used on the bard.
Credit: Sean K. Reynolds

Clerics
Clerics and Holy Warriors are able to spontaneously cast spells.  

Druids
Druids get proficiency in shortbow.  Wild Shape ability lasts 1 minute/level.
Credit: Sean K. Reynolds

Sorcerers
Sorcerers can swap out one spell each time they gain a sorcerer level. Sorcerers do not have a casting time increase when using metamagic feats.
Credit: Sean K. Reynolds

Wizards
A wizard can only use her bonus feats on item creation feats or Spell Mastery, not metamagic feats. All wizards must take a specialist school of magic.  Wizards gain the Spontaneous Casting: Cantrip Mastery feat free at 3rd level. 

Spontaneous Spellcasting
Divine spellcasters (clerics, druids, holy warriors) in Theeurth do not need to prepare their spells.  They must still spend time in prayer or meditation.  Each has a spell list unique to their deity.

Wizards may gain spontaneous spellcasting through the Spontaneous Spellcasting series of feats.

Specialist Bonus
In addition to the features of specialist wizards described in the PHB, wizards cast spells within their school of specialization as if they were one level higher than their actual caster level.  This may affect such variables as damage, range and duration, as well as any other effect based on caster level.

Skills and Feats

Concentration Skill
Casting defensively using the Concentration skill has a DC of  the threatening character's attack roll + the spell level.   So a wizard casting invisibility standing next to an ogre must make a check based on the ogre's attack roll plus 2 for the 2nd-level spell (d20 + 8 attack + 2 for spell level). This mechanic often makes this check harder, except when fighting very weak opponents.
Credit: Monte Cook

Craft (Alchemy) Skill
The Craft (Alchemy) skill allows a chance (DC 15+minimum caster level of potion) to identify common potions by taste or smell.

Intimidate Skill
Intimidate is a class skill for Fighters.  Characters may choose to add either their Strength modifier or their Charisma modifier to Intimidate rolls.

Sneak Skill
The Hide and Move Silently skills are combined into a single skill: Sneak.  All bonuses to either Hide or Move Silently under the standard rules apply to a character's Sneak skill.  
Credit: Monte Cook's Unearthed Arcana

Spellcraft Skill
In order to recognize a spell being cast or to recognize a spell by its effects after it has been cast, the DCs are as follows:

• For spells known by viewer: DC 10 + the level of the spell
• +5 for spells not known by the viewer
• +5 for spells from a restricted school or other realm of magic.
• +5 for rare spells (unless known by viewer)
• +1 per for every 5' (rounded up) over 30' distant to the caster

Disallowed Skills
Theeurth games no longer uses the Use Magic Device skill.  If you want to use Magic devices, take levels in the appropriate classes. 

Toughness Feat
Grants +1 hp/level.  

Item Creation Feats
Item Creation Feats work somewhat differently in Theeurth than in standard D&D.  The Item Creation page is here.

Disallowed Feats
The following feats simply do not exist in Theeurth:

• Leadership
• Sudden Metamagic
• Divine Metamagic

Combat

Reach Weapons
Characters wielding a reach weapon may attack foes within 5', but at a -4 penalty to hit and a -4 penalty to damage.  In addition, attacking a target more than 5' away, including as an Attack of Opportunity, will trigger an Attack of Opportunity for any enemy that is less than 5' away.

Spear and Shortspear
The spear and shortspear are both treated as if one size category smaller when wielded by characters with martial weapon proficiency.  Thus, a small Fighter can wield a shortspear one-handed and a medium Fighter can wield a spear one-handed.

Heavy Crossbow
Heavy crossbows function as described in the Player's Handbook except that within 1 range increment, heavy crossbows ignore 2 points of armor bonus to the target's AC. 
Credit: The Lich's Lair

Flanking I
Whenever any character is Flanked, he is Flanked as to every adjacent enemy, not merely to those who cause him to be Flanked.

Flanking II
You can disregard attacks from an opponent flanking you. When you do, that opponent doesn't get the +2 flanking bonus when attacking you and that opponent does not provide a flanking bonus to any of its allies. Ignoring a flanker, however, provokes an attack of opportunity from that flanker, and you lose your Dexterity bonus to Armor Class against that flanker. You do, however, continue to threaten that flanker.

If the flanker is out of attacks of opportunity, you can ignore the flanker (and deny the flanking bonus) with impunity.

If you can't see (or locate) the flanker, you disregard the flanker by default, and you provoke the attack of opportunity.

You must make the decision to disregard a flanker as soon as the foe moves into a flanking position. You can change your decision as a free action on your turn. (You still must disregard a flanker you can't see.)
Credit: Skip Williams, Jonathan Tweet

Firing into Melee
Anyone may choose to ignore the -4 penalty for shooting into combat (but not any penalties for cover). However, if the unmodified die roll is a 1, 2, 3 or 4, the arrow has hit an unintended target.  The GM will determine which creature in melee with the target was struck.

Death and Dying
In the description below, M equals the Constitution Modifier, if greater than 0.  Otherwise, it is 0.  C equals the Constitution score.

• If a character has at least 1 hit point, he can act normally.
• Between 0 and -M, he is disabled.
• From -M to -C he is dying.
• Below -C, he is dead.

When a character is Disabled, he is not quite unconscious, but almost.  He may take one standard action or one move action per turn, but any strenuous activity (spellcasting, combat, etc.) causes him to lose one hit point.  A disabled character makes all attack, damage, saving throws and skill checks at a -2 penalty.

When a character is dying, he immediately falls unconscious.  Each round, he must make a stabilization check.  This is a percentile (d100) roll.  If the roll is equal to or less than his Constitution, the character becomes stable.  If not, he loses 1 hit point.  If he reaches a number lower than -C, he dies.

A conscious character may stabilize a dying character with a Heal check with a DC equal to (10+the dying character's negative hit points).  For instance, the DC for a character with -8 hit points is an 18.  Even 1 hit point of magical healing will stabilize a dying character.

Stable Characters and Recovery
If made stable by another (with a successful Heal check), an hour after becoming stable, a character may roll a consciousness check. This is a percentile (d100) roll.  If the roll is equal to or less than his Constitution, the character becomes disabled and conscious.  Otherwise, the stable character can make another roll each hour.  Even unconscious, stable characters recover their hit points at the normal rate, and return to consciousness when his points rise to 1 or higher.

If the character stabilizes on his own, via a stabilization check, but has no one to tend him, he still loses hit points, but at a slower rate.  The character has a percentage chance every hour equal to his Constitution score of becoming conscious.  Each time he misses this hourly roll, he loses 1 hit point. The character also does not recover hit points from natural healing.  

Even once the character becomes conscious and disabled, he will still not recover hit points naturally if untended.  Instead, each day the unaided character has a percentage chance equal to his Constitution to begin recovering hit points naturally (starting with the day he regains consciousness), otherwise, he loses 1 hit point.  Once an unaided character starts recovering hit points naturally, he is no longer in danger of losing hit points (even if his current hit point total is negative).
Credit: Monte Cook's  Arcana Unearthed, pp. 150-151.

Natural "1"  or "20" in Combat
A natural roll of "1" is not automatically a miss, nor is a natural roll of "20" automatically a hit.  A natural one is considered to be equal to a roll of -10 and a natural 20 is considered to be equal to a roll of 30.  If a roll of -10 (plus modifiers) would still hit, then the roll is a hit.  If a 30 (plus modifiers) would still miss, then the roll is a miss.

Whenever you roll a natural 1 to hit in combat your attack sequence immediately ends and you forfeit any remaining attacks for the round.
Credit: Unearthed Arcana, modified

Two Natural "20's"
Whenever a character rolls a natural 20 to hit and a natural 20 to confirm the critical, the resultant hit does maximum critical damage (assuming the target is not immune to critical hits).  This does not include any additional damage such as that rolled for a sneak attack.
Credit: Peter Drake

Magic

Detecting Alignments
Alignments simply cannot be detected by any mortal power or spell.

Non-Automatic Remedies
Remove disease, neutralize poison, remove blindness/deafness, remove paralysis , and remove curse are no longer automatically successful. Using these spells in Theeurth involves a caster level check, similar to that used with dispel magic. For diseases, poisons, curses, blindness, and so on that result from a spell, the cleric must make a d20 check, adding his own caster level. The Difficulty Class for this check is 11 plus the level of the original caster. 

For afflictions that do not result from a spell, such as wyvern poison or mummy rot, use the saving throw Difficulty Class of the poison, disease, or other malady as the Difficulty Class for the caster level check.
Credit: Monte Cook

Returning from the Dead
Returning from the dead has long been a staple of D&D.  However, this fact can cheapen death, making it more of an inconvenience than the ultimate penalty or sacrifice.  On the other hand, removing it entirely from the game can reduce the fun of the game when a long-standing character suddenly dies by a trivial accident of the dice.  Therefore, such spells as Raise Dead, Resurrection and True Resurrection do exist, but are limited as follows:

In all cases, the spells which return the living from death are neither easy to cast nor lightly granted by the gods.  First, the casting of all such spells now requires a full day. Second, the gods will permit this only in rare instances, such as if the deceased fell as a direct result of a quest given to him by the church in question, or if the deceased was a great friend of the church.  Third, any such casting requires rare and difficult-to-obtain components, treasures and the object of quests in and of themselves.

Disallowed Spells
The following spells simply do not exist in Theeurth:

• Disjunction / Mordenkainen's Disjunction
• Gate
• Any form of shapechanging (alter self, polymorph, shapechange, etc.)
• Heroes' Feast
• Energy Immunity
• Time Stop

Disallowed Magic Items
The following sorts of magic items simply do not exist in Theeurth:

• Metamagic rods
• Rod of absorption

The Identify Spell
Identify has been replaced in Theeurth games the following:

Identify
Divination
Level: 1
Casting Time: Varies
Range: Touch
Target: One Magic Item 
Duration: Instantaneous
Saving Throw: None
Spell Resistance: No
Components: V, S, M/DF (Focus)

Through careful study of a magic item, you learn one of its abilities that you did not already know, and how to activate it. If you know all the item's capabilities, then you learn that fact as well.  Either way, you also learn the number of charges or uses the item has. Successful casting of this spell requires a Knowledge (Arcana) check, with a DC set by the GM.

The spell takes 15 minutes to cast on a potion or similar one-use item if the item is of a common sort (determined by the GM).  Rarer potions or one-use items may take longer, up to an hour each.  If the identification takes less than an hour, multiple such items may be identified so long as the total time does not exceed an hour.  Thus, up to four potions or common one-use items may be identified with a single casting of this spell.

More complex items will take proportionally longer to identify (at the GM's discretion) and only one may be thus identified with the spell.  A simple Wand of Fireballs may take an hour, while it may require a whole day to puzzle out a single use of a very rare or complex item.  

The spell requires the use of a special lens, prism, crystal or set of goggles costing 250 Traders.  This focus is reusable.

The Mind Blank spell
This spell no longer cancels mind-affecting spells.  It continues to block all divinations as before.

Scrying
Scrying uses the following DCs instead of those presented in the PHB:

*If the target is on another plane, increase the DC by 5.
**You must have some sort of connection to a creature you have no knowledge of.

Opposed Scry Checks

A character with Scry skill is more proficient than most at detecting the scrying sensor when he is the subject of a scrying effort.    He may make an opposed check against the scrying character, with a modifier of (20-DC of initial scrying attempt).
Credit: Andy Collins and Monte Cook

Miscellaneous

Masterwork Items
Masterwork items cost five times as much as standard items, or an additional 300 T., whichever is more.

Falling Damage
Falling is quite dangerous, and long falls can be fatal at any level.   No damage is taken for a five foot fall.  For every five feet beyond that, 1d6 damage is taken.  Of that, the first 1d6 is subdual damage while the rest is normal damage.  Characters are allowed a Reflex saving throw to suffer only half damage.  The DC of the save is equal to the full amount of damage taken if the save fails.  Evasion does not add to this saving throw.

In addition to hit point damage, falling characters suffer 1d6 Constitution damage and 1d6 Dexterity damage for every fifteen feet fallen (beyond the first fifteen feet).  This damage may also be halved on a successful Reflex saving throw.  

If the landing is on a soft surface (mud or soft ground), the second die of damage is also subdual damage.  

If the character deliberately jumps, another die of damage is converted to subdual damage (this is cumulative with the die for a soft landing).  In addition, if the Reflex save is made, subtract ten feet from the total distance fallen.

 If the fall is into water at least ten feet deep, subtract twenty feet from the distance fallen and the character suffers only 1d3 of subdual damage per each ten feet of the next twenty feet (i.e., a character falling forty feet into twenty feet of water suffers only 1d6 of subdual damage).  Beyond that, assess normal falling damage.  This is cumulative with the bonuses for jumping, but not with a soft landing.

A character who dives into water that is at least one-third as deep as the fall (or forty feet deep, whichever is less) may avoid all damage on a successful Swim or Tumble check.  The DC of the check is 15 plus1 per ten feet in the dive (modified for encumbrance).

Hero Points
Hero points reward characters for selfless acts and brave deeds.  They are awarded at the GM's discretion but may be used at the player's discretion to perform amazing or even otherwise impossible deeds.

Awarding Hero Points - Hero points will be awarded only when the GM feels that the PC has acted heroically and selflessly.  Self-interested deeds, regardless of how amazing, will not gain Hero Points, nor will any action performed with a Hero Point.  Cautious PC's, even the most well-played, may never earn a single Hero Point.

Using Hero Points - On his turn, before determining the success or failure of an action, a player can announce that he is using a Hero Point to help accomplish the action.  Normally, the Hero Point add a bonus of +20 to the action, if the roll of a d20 dictates its success or failure.  However, there are exceptions:

1. If used with an attack roll, and the attack roll would have succeeded without the Hero Point, the Hero Point doubles the damage inflicted by the attack OR it allows the PC to make a "called shot" inflicting a special effect such as:
   • A strike to a foe's eyes that blinds him for 1d10 +4 rounds.
   • A strike to a foe's head or other vitals that stuns him for 1d3 rounds.
   • A strike to a foe's limb that renders it useless for 1d6 rounds

    

2. If a character uses a Hero Point to act when it is not his turn, he can take a normal round's worth of actions out of the normal initiative sequence with no special bonuses.  He then returns to his normal initiative count.
3. If used when a character is being attacked by either a physical attack, a spell or some other threat, the Hero Point can be used to add a +1d20 luck bonus to Armor Class or to a saving throw.  If used with a saving throw for half damage or partial effect, if the character would have made the save without the Hero Point, he takes no damage or ill effect at all.
4. If used when a die roll determines that the character will die, the character avoids death and instead suffers a great and debilitating injury determined by the GM - the character gains a disfiguring scar, loses a hand, loses an eye, gains a limp, and so on.  This is the only case when a Hero Point can be used after the result of an action is determined.
5. A character can use a Hero Point to make something work in a way the rules normally do not allow.  This requires careful GM adjudication.  For example, a wizard could use a Hero Point to cast a special version of Petrification that turned a foe to stone for only one hour (instead of permanently) or that could be undone only by some specific requirement  (the touch of three honest thieves, or exposed to the light of heaven, for example).  A fighter might try to use a Hero Point not only to disarm a foe but to send the weapon sailing into the hand of a nearby ally.

The GM will still apply all normal circumstance modifiers to the PC's action.  Actions using Hero Points can still fail. 

Hero Points for NPCs - Players are on notice that NPCs, including villains, may also have Hero Points to use.
Credit: Monte Cook, Arcana Unearthed