Spellthief's Steal Spell-like ability -- How do I determine level of ability?

[Talionis]

I'm uncertain about how to determine the powerlevel of a spell-like ability.

1. How do I know what level it is?
2. Is there a way to increase the level of spell-like ability I can steal? Beyond just taking more levels of Spellthief...
3. What spell-like abilities are the best abilities to go after? I was wondering if summoning creatures to steal their spell-like abilities was useful.

Wizards has been nice enough to post the complete description of Spellthief: http://www.wizards.com/default.asp?x=dnd/ex/20050107a


Quote: Steal Spell-Like Ability (Su): At 5th level and higher, a spellthief can use a sneak attack to temporarily steal a creature's spell-like ability. A spellthief who hits an opponent with a sneak attack can choose to forgo dealing 1d6 points of sneak attack damage and instead gain one use of one of the target's spell-like abilities. If the target is willing, a spellthief can steal a spell-like ability with a touch as a standard action.

This spell-like ability can originate from the target's class, race, template, or any other source, and can be of any level up to a maximum of one-third the spellthief's class level. A spellthief can select a specific spell-like ability to steal; otherwise, the DM chooses the ability at random. If the ability has a limited number of uses per day, the target must have at least one such use left, or the spellthief can't steal the ability. If the target can't use its ability at the present time (such as a summoned demon's summon ability), the spellthief can't steal it.

A spellthief can use a stolen spell-like ability once. For all purposes (caster level, save DC, and so on), treat the spell-like ability as if it were being used by the original possessor of the ability. A spellthief must use the stolen spell-like ability within 1 minute of acquiring it, or it is lost harmlessly. Until the spellthief uses the ability (or until the minute elapses), the target cannot use the stolen ability.

[Ravens_cry]

Spell like abilities are, well, like spells, so, look up what level the original spell is cast at?
That would be my guess any way.

[Flickerdart]

SLAs that don't replicate spells usually list their level equivalency.

[Talionis]

I'm still trying to figure out if there is a way other than more levels of spellthief to increase my Steal Spell-like ability? Anyone have suggestions.

Here is an answer I found at Roleplay Nexus it looks pretty legit for figuring out level of a spell-like ability: http://www.roleplaynexus.com/errataspelllike.html

Determining a Spell Level for a Spell-Like Ability

It's often necessary to determine what level spell a spell-like ability duplicates. For example, you'll need to know the spell level whenever someone uses a detect magic spell to study a spell-like ability's ongoing effects. Also, as noted earlier, you'll often need to know the ability's level to determine the DC for any Concentration check the user might have to make when employing the ability.

The spell level also affects the saving throw DC for the spell-like ability, but that information usually is included in the user's creature description.

Exactly what level spell a spell-like ability duplicates often proves unclear, because most spells become available to casters of different classes at different levels. To determine the spell level for a spell-like ability, always use the level for the sorcerer/wizard version of the spell. If the spell has no sorcerer/wizard level, use cleric, druid, bard, paladin, or ranger level, in that order. Sometimes a creature's description will specify a kind of caster for the creature's spell-like abilities. If this is so, use the appropriate level for the spell-like ability.

You also can calculate a spell-like ability's level from the saving throw listed for it. Simply subtract 10 + the user's Charisma modifier from the listed DC and the result is the ability's spell level.

As noted earlier, some spell-like abilities don't duplicate spells. For example, a paladin's ability to call a special mount is a spell-like ability gained at 5th level. This ability is very similar to the 1st-level mount spell and can be treated as a 1st-level effect.

Here were some other good links for Spell-Like Ability information:

http://www.wizards.com/default.asp?x=dnd/rg/20040413a

http://www.wizards.com/default.asp?x=dnd/rg/20040420a