My DM has foolishly allowed me to play a Serpentfolk, advanced, from Bestiary 2 (p.242). Just a quick rundown:
Stats: -2 Str, +10 Dex, +6 Con, +8 Int, +4 Wis, +6 Cha; scaling spell resistance, two spell-like abilities at 4th (dominate person & major image) and 9th char level (mass suggestion & teleport). They also get a bite attack with poison, fort save DC is 10 +con mod +1/2 HD or they lose 1d2 str; cure 2 saves.
Class ideas on how to best make use of this? We're almost certainly going to play the Kingmaker AP next.
I'm just finishing playing a wizard so I'm not sure I want to play another pure spellcaster right away. I'm playing a conjurer now, so I could possibly be open to a blaster.
I am in the middle of the Hellknight Pathfinder novel so I'm finding that Prestige Class pretty interesting.
Unless you are soloing the AP, that stat block will make the game no fun for anyone else. Could play as a Commoner and ruin it for the rest of the party. Are you sure he did not mean to allow Lizard Folk or Nagaji? Also, calling the DM foolish is a total lack of respect.
as long as they are allowing others to take similar options there should be no issues, however issues will arise if they allow one player to do something like this and not give any other players the option to do so.
Class ideas on how to best make use of this?
Write a concept, figure out the details, probably try it against a few NPCs on your own - then put it into a drawer and keep it there. Because it ruins the fun of your fellow players, then the fun of your GM and finally your own - and be it just because the campaign is shut down.
Maybe I miss some context and the other players control characters of similar power level, while the GM adapts challenges accordingly. But it doesn't sound like it.
That depends, do you want to be fair and let other characters shine? If that's the case, choose whatever you think sounds cool and don't worry about getting the most out of it. Those amazing stats will help with any deficiency, so while you won't be min-maxed, you won't be a hindrance either. If you want to be a total hardcore over the top boss, go dex-based Magus or Warpriest.