Casting first in defence + endgame spells

[IndyPendant]

Heh. I was the attacker in question, and I'm still rather annoyed about the whole thing. (Not at Twan, note. At this particular mechanic.) I basically wasted untold hours of complicated end-game turns, because evicting Twan was so incredibly, unbelievably unlikely that I might as well have gone AI shortly after he took the island. Even destroying the rest of his territories would have taken so long that by the time I was done he would have had his nigh-impenetrable defenses up on the central island...

It all came down to the defender casting first.

To answer some of the points brought up: spells cannot get past domes. Assassins and disease-spreaders cannot get past patrollers. Multiple attackers do not work against a castle. There was essentially no reasonable method, at all, of evicting him. Period.