Shade
Monster Junkie
I forgot about this conversion. 
Give it the spellcasting ability of a 12th-level wizard, or spell-like abilities based off a similar list?

A new False Keraptis can generate spell effects as a 12th-level wizard, in addition to using his or her regular powers and abilities. At the time of imprinting, the DM must choose a daily complement of spells (four 1st-level, four 2nd-level, four 3rd-level, four 4th-level, four 5th-level, and one 6th-level) for the new pretender. Available choices include spells from the character’s own spellbook or priest sphere (if applicable), plus the following list, which represents the contents of the original wizard’s spellbook: 1st-charm person, K: complete imprint*, magic missile, sleep, wizard mark; 2nd-acid arrow, continual light, darkness 15’ radius, ESP, knock, magic mouth, mirror image, wizard lock; 3rd-dispel magic, fireball, fly, lightning bolt, monster summoning I, slow, tongues; 4th-charm monster, dimension door, enchanted weapon, Evard’s black tentacles, ice storm, improved invisibility, monster summoning II, polymorph other, polymorph self, stoneskin, wind wall, wizard eye; 5th-advanced illusion, cloudkill, cone of cold, conjure elemental, dismissal, monster summoning Ill, true seeing, force, wall of stone; 6th-contingency, death fog, death spell, globe of invulnerability, monster summoning IV, Tenser's transformation. (Spells of 7th level and higher become available to a False Keraptis who reaches a level high enough to be able to cast them.) Once the DM has decided upon a spell selection, it becomes permanent. (No such choices exist for a husk who becomes the new seat of an existing hierarchical mind; he or she simply assumes the existing spell complement.)
Give it the spellcasting ability of a 12th-level wizard, or spell-like abilities based off a similar list?