Just an idea of mine - the Dom3 Q&A thread

[Endoperez]

Taqwus said:
If the banefire's Decay effect is not resisted, there usually won't be any "after the battle" for the affected units.

At least in Dom 2, Decay was survivable IF you had very, very high regeneration and base hp, but otherwise, you'd die -- it'd iterate through turns of damage and kill you.

It ages the target in Dom3. I don't know how much, but I quess it won't kill now, at least not directly.