Though that's funny only if we actually can't kill one.
I thought about it, wouldn't we able to kill at least
the smallest one if, in theory, we'll:
1. Get everyone Cold Iron weapons, including Cold Iron arrows.
2. Buff everyone or most of our fighters through potions of Ablative Barrier, Barkskin, Bear's Endurance, Bull's Strength, Cat's Grace (I hope we'll be able to get the last four from Ohun for Zaia to study and brew), Enlarge Person (this we can get for Inge on her level-up, though I hope we'll be able to get it for Zaia from somewhere).
3. Be level 6?
4. Use Drums of Haste.
5. Max out front-line combatants' shield AC bonus to +4 through Shield extract.
6. Successfully immobilize it though webs and entanglement with nets and ropes and evade it's breath weapon.
Cold Iron would stop its regen, and if we'll be succeeding on a sufficient number of attacks each round we'll kill it fast and it won't be able to deal enough damage to kill any of our guys.