Nar Demonbind
Lost Empires of Faerun, pg 32.
Level: Cleric 7, sorcerer/wizard 7
Casting Time: 1 hour
Range: Touch
Target: Humanoid with Intelligence 4 or higher
Duration: Instantaneous
Save: Will Negates
SR: Yes
Material component: Gems with a total value equal to the XP cost
XP Cost: 500 XP/level of the subject
Benefit: Touched subject gains the
half-fiend template.
Permanently.
Treat it as an acquired template, rather than inherited.
You become an outsider, your alignment changes to evil.
You also gain the +4 level offset.
The catch: You cannot cast this spell on yourself.
...However, I see nothing that prohibits you from ordering your cohort to cast it on you.
Or ordering your cohort to let you cast it on them.
Further FYI: The cost of handing a scroll of this you scribed to a hired caster when you are level 20? 60,910 gp
Not bad for buying a template, IMO.