I'm gonna dump a copy of my Fiend of Possession build notes here. Feel free to give advice or point out any mistakes. I'm going for a build suitable for larger groups. Able to be dropped into the background and still be helpful.
Diabolus (+1LA)
Divine Minion- Sebek (+1LA)
*Cloistered Cleric-1
-(Travel+ Knowledge Domains?)
Ardent-2
- Guardian and Life. Look into others.
Fiend of Posession-6
-(Fiend Folio pg204)
FEATS-
Flaw1- OPEN
Flaw2- OPEN
HD1-*Martial Study -shadow hand
HD3-Practiced Manifester
HD6- OPEN
HD9- OPEN
STATS-
Cha- For FOP saves.
Wis- Casting Stat. Shapesand too!
Con- HP and Concentration skill.
Int- FOP hide! Maybe above Con?
Dex- Meh.
Str- Meh meh.
SKILLS-
Get Hide and KNow: Arcana to 6 ASAP.
NOTES-
*may be traded for Swordsage and Educated
feat instead. 2 SS levels for wis to AC in gator form?
-Lots of turning and wildshape. Take
feats to utilize those.
-Limited powers known. boost this somehow.
-Find some way to communicate as an item.
Psionic power maybe?
-Use feats to boost FOP DCs.
-LA buy off is a good idea @ lv6 and lv9.
