All of the following are class features of the spellthief.

Weapon and Armor Proficiency: Spellthieves are proficient with all simple weapons and with light armor but not with shields. Because the somatic components required for spellthief spells are simple, a spellthief can cast spellthief spells while wearing light armor without incurring the normal arcane spell failure chance. However, a spellthief wearing medium or heavy armor or using a shield incurs a chance of arcane spell failure (see page 123 of the Player's Handbook) if the spell in question has a somatic component (most do). A multiclass spellthief still incurs the normal arcane spell failure chance for arcane spells received from other classes, including those stolen from arcane casters (see the steal spell ability, below).

Sneak Attack (Ex): A spellthief deals an extra 1d6 points of damage when flanking an opponent or at any time when the target would be denied its Dexterity bonus. This extra damage applies to ranged attacks only if the target is within 30 feet. It increases to 2d6 points at 5th level, 3d6 points at 9th level, 4d6 points at 13th level, and 5d6 points at 17th level. See the rogue class feature, page 50 of the Player's Handbook. If a spellthief gets a sneak attack bonus from another source (such as rogue levels), the bonuses on damage stack.

Steal Spell (Su): A spellthief can siphon spell energy away from his target and use it himself. A spellthief who hits an opponent with a successful sneak attack can choose to forgo dealing 1d6 points of sneak attack damage and instead steal a spell, or the potential to cast a specific known spell, from his target. If the target is willing, a spellthief can steal a spell with a touch as a standard action.

The target of a steal spell attack loses one 0-level or 1st-level spell from memory if she prepares spells ahead of time, or one 0-level or 1st-level spell slot if she is a spontaneous caster. A spontaneous caster also loses the ability to cast the stolen spell for 1 minute. If the target has no spells prepared (or has no remaining spell slots, if she is a spontaneous caster), this ability has no effect. A spellthief can choose which spell to steal; otherwise, the DM determines the stolen spell randomly. If a spellthief tries to steal a spell that isn't available, the stolen spell (or spell slot) is determined randomly from among those the target has available.

For example, a 1st-level spellthief who uses this ability against a 1st-level sorcerer could choose to steal magic missile. Assuming the sorcerer knew that spell, a successful steal spell attack would eliminate one 1st-level spell slot and temporarily prevent her from casting magic missile. If the same spellthief stole magic missile from a wizard who had it prepared, the wizard would lose one prepared magic missile spell (but wouldn't lose any other magic missile spells she might also have prepared).

After stealing a spell, a spellthief can cast the spell imself on a subsequent turn. Treat the spell as if it were cast by the original owner of the spell for the purpose of determining caster level, save DC, and so forth. A spellthief can cast this spell even if he doesn't have the minimum ability score normally required to cast a spell of that level. The spellthief must supply the same components (including verbal, somatic, material, XP, and any focus) required for the stolen spell. Alternatively, a spellthief of 4th level or higher can use the stolen spell power to cast any spellthief spell that he knows of the same level or lower (effectively, this gives the spellthief one free casting of a known spell). A spellthief must cast a stolen spell (or use its energy to cast one of his own spells) within 1 hour of stealing it; otherwise, the extra spell energy fades harmlessly away.

As a spellthief gains levels, he can choose to steal higher-level spells. At 4th level, he can steal spells of up to 2nd level, and for every two levels gained after 4th, the maximum spell level stolen increases by one (up to a maximum of 9th-level spells at 18th level).

At any one time, a spellthief can possess a maximum number of stolen spell levels equal to his class level (treat 0-level spells as 1/2 level for this purpose). For instance, a 4th-level spellthief can have two stolen 2nd-level spells, or one 2nd-level spell and two 1st-level spells, or any other combination of 0-level, 1st-level, and 2nd-level spells totaling four levels. If he steals a spell that would cause him to exceed this limit, he must choose to lose stolen spells sufficient to reduce his total number of stolen spell levels to no more than his maximum.

A spellthief can't apply metamagic feats or other effects to the stolen spell unless the specific spell stolen was prepared with such an effect. For example, a spellthief of 6th level or higher could steal a wizard's empowered magic missile, but only if he specifically chose to steal empowered magic missile. If he chose to steal an unmodified magic missile, he couldn't steal an empowered magic missile, a silent magic missile, or any other metamagic form of the spell. A spellthief couldn't steal an empowered magic missile from a sorcerer, since the sorcerer applies metamagic effects upon casting and thus has no prepared empowered magic missile spell.

This ability works only against spells. It has no effect on psionic powers or spell-like abilities (but see the steal spell-like ability class feature, below).

Trapfinding (Ex): A spellthief can use the Search skill to locate traps with a DC higher than 20, and he can use Disable Device to bypass a trap or disarm magic traps. See the rogue class feature, page 50 of the Player's Handbook.

Detect Magic (Sp): A spellthief of 2nd level or higher can use detect magic a number of times per day equal to his Charisma bonus, if any (minimum 1). His caster level is equal to his spellthief class level.

Spellgrace (Su): A spellthief of 2nd level or higher gains a +1 competence bonus on his saves against spells. This bonus improves to +2 at 11th level and to +3 at 20th level.

Steal Spell Effect (Su): Beginning at 2nd level, a spellthief can siphon an active spell effect from another creature. A spellthief who hits an opponent with a sneak attack can choose to forgo dealing 1d6 points of sneak attack damage and instead gain the effect of a single spell affecting the target. If the target is willing, a spellthief can steal a spell effect with a touch as a standard action.

The spellthief can choose which spell effect to steal; otherwise, the DM determines the stolen spell effect randomly. If a spellthief tries to steal a spell effect that isn't present, the stolen spell effect is determined randomly from among those currently in effect on the target. A spellthief can't steal a spell effect if its caster level exceeds his class level + his Charisma modifier.

Upon stealing a spell effect, a spellthief gains the stolen effect (and the original creature loses that effect) for 1 minute per class level (or until the spell's duration expires, whichever comes first). If the spell effect's duration hasn't expired by this time, the spell effect returns to the creature that originally benefited from it.

A spellthief can steal the effect of a spell only if the spell could be cast on him by the original caster. For example, a spellthief couldn't gain the effect of an animal growth spell (unless the spellthief is of the animal type) or the effect of a shield spell (since that spell's range is personal). If a spellthief tries to steal the effect of a spell not allowed to him, the effect is still suppressed on the original target of the spell for 1 minute per spellthief class level.

This ability does not work on spell effects that are immune to dispel magic (such as bestow curse).

Steal Energy Resistance (Su): Beginning at 3rd level, a spellthief can siphon off some or all of a target's resistance to an energy type (acid, cold, electricity, fire, or sonic). A spellthief who hits an opponent with a successful sneak attack can choose to forgo dealing 1d6 points of sneak attack damage and instead temporarily gain resistance 10 to an energy type to which his target is resistant or immune). If the target is willing, a spellthief can steal energy resistance with a touch as a standard action.

Simultaneously, the target creature's resistance to that energy type is reduced by 10 (to a minimum of 0). A creature with immunity to an energy type retains that immunity.

If his target has more than one type of resistance to energy, a spellthief can choose which kind to steal; otherwise, the DM determines the stolen resistance randomly from among those possessed by the target. If a spellthief chooses to steal a type of resistance that the target doesn't possess, the stolen type of resistance is determined randomly from those possessed by the target.

The resistance a spellthief gains from using this ability lasts for 1 minute. If the resistance is derived from a temporary effect (such as a spell), the stolen resistance disappears when the effect expires.

A spellthief can use this ability multiple times, but its effects do not stack unless they apply to different types of energy. For example, throughout a long combat, a spellthief might use this ability to gain resistance to fire and resistance to cold, but he could not use it twice on a creature tha