Trickster
The typical spellthief is essentially a rogue who can steal magic, and as a related endeavor can cast a few spells as well. By taking the trickster ability substitution, a spellthief becomes more a sorcerer who has learned to draw magic from others as well as from an internal heritage. This is the most sweeping of these ability substitutions, and it should appeal to players looking for an arcane spellcaster with a broad range of new tricks.
Level: 1st.
Replaces: You lose 2 skill points per level. You gain only 4 skill points + Int modifier at each additional level (x 4 at 1st level). In addition, Appraise, Bluff, Disable Device, Escape Artist, Hide, Jump, Move Silently, Open Lock, Search, Swim and Tumble are no longer class skills for you.
You do not gain the trapfinding ability at 1st level.
You do not gain additional sneak attack bonus dice at 4th or higher levels. Your spellthief sneak attack bonus damage remains fixed at +1d6. If you have other classes that grant more sneak attack bonus dice, you gain those as normal.
Benefit: You cast spells as a bard of your spellthief level, and your caster level equals your spellthief level (rather than half your spellthief level). You gain spells per day and spells known as a bard of your level, which allows you to cast spells at 1st level, unlike a typical spellthief. In addition to the spellthief spell list, you may select spells known from the bard spell list as well