Under normal circumstances, they won't have time to react; the initiative of the demons is 13, which almost guarantees this, but you can try to kill them with fast units, for example, Imps... in this case, it won't be possible to hide them due to the acid breath.
Imps might not even reach them. If they are standing in different corners. For example, that's how it would be for me. Because my priority is still the enemy archers.
So you fall at his feet hes the one who betrays you
Its the servants devotion for the decay
Stand up
There are no flowers on your grave
There are no chains
There I keep chanting for the forgotten name © Amorphis