- Venom Crab
Usually around 10-20 hp, needs close range to attack, will add up poison stacks on your party members (-AC / -hp per round).
These die easily, but there is usually a big number of them. Fortunately they are vulnerable to mental magic, so your bard’s lute as well as spells like Terror or Insanity will be great against them.
Also, they take good damage from fire realm spells, as expected.
If you have a source of area damage, that too will be a good idea.
And as you probably thought they would be: They are pretty resistant to water magic. So if you are just so-so with your paralyze spell, spare your round and your spell points.
Kill them whenever you have time for that in the group after the Monastery. They are not a number one priority, but they are bothersome nonetheless!
- Hardshell Crab
Going up to around 40 hp these are harder opponents and should be your number one targets as they have extended range. If you have casters or other weaklings in the second row, you should not come close to them but rather kill them from extended range.
They can hit pretty hard, usually double digits and are generally not easy to deal with when your party is still low level.
As for spells, go with the Venom Crab advice above: Weakness to mental and fire spells. Insanity is great on these.
- Soldier Ant
Usually only around 20 hp and in large groups, they hit pretty hard and can fit into one spot easily. Their models don’t need much room, so on a minimal door, there would even fit 2 or 3 of them, like you encountered with the roaches and other bugs. They can hit pretty hard and you should kill them quickly because it is so easy and they do some significant damage for their low hp score.
You will likely have some source of area damage right now; use it against them. Also, mental spells will be great against the ants.
Don’t let yourself get surrounded, as this will likely be fatal for your casters or other back row characters. Use at least the “your back to the wall” tactic!
Have fun gaming!