[lch]

1. is being asked countless times... it's just flavor text. On top of the Behemoth, there's some guy. Description says that it's a death mage. Some smart guy might say that he wants the death mage to cast spells in combat, then, flavor text says no deal.

2. the only thing that poison does is stick to a unit like fatigue. Damage is done separately, the manual explains how. For the supposed tactic, this would be frowned upon in MP gaming. The skellies will dissolve when the marshmaster leaves the battlefield, too, more or less instantly. You won't kill too much with this, I think, because then Foul Vapors is cancelled and given how poison does its damage over time.