I completely disagree with those who think they can just bombard the Swamp in its own castle. After destroying the catapult and the supply cart, you can just keep using the "Gap" ability for all 24 rounds while some Archmage keeps shooting at you. Not to mention that it deals only 1/4 damage.
Well, I slightly disagree here.
-Archmages ignore wall penalties.
-and the main thing is to have the "Gap" ability at the beginning; after that, you can use it infinitely.
But overall, I completely agree! The Swamp is a tank. Attacking it without powerful magic is like courting death!