Are mist monsters a priority?

should i kill them first or crabmen and such.

Last. As long as you don’t get too close to activate them. Then do them first. Preferably clear the mist with explosives too.

okay ty, i always go for them first, how many times can they expand mist?

As far as I know they’ll do it about every three turns and just keep going. Stay about 5 or more squares away to not activate them and save ammo for other things. Then you can a) save crates for the next build and the crabbies go after the crates b) save ammo to use on the creatures and not exhaust clips of better stuff. It makes the end of the round a bit more relaxing after swarms of mindfraggers and grenadiers.