Suggestions? FPS dips to low 20.

what's your system? graphics settings? is there anything in particular happening that corresponds to those fps dips?

 

some spell effects are generated so inefficiently (possibly requiring a disk I/O read or something) that they will always cause fps hits for me: mirror image is the biggest culprit here for me.

 

there's also a subtle memory leak - if you reload the game in the middle of combat (e.g. if events take a wrong turn), some things don't get properly flushed out of memory in the game engine, so the more you do this, the lower your overall frame rate, ESPECIALLY in combat. you can solve this by periodically quitting to the game menu and loading a game that way, instead of reloading a game directly from within an existing game. (historical note: i believe this was also responsible for some terribly amusing bugs in the past, such as implosion charge playing its suction sound on loop over and over even through game reloads, or ship morale going up or down by ginormous amounts because the game forgot to reset your ship combat attempts if you reload in the middle of a ship fight)