The name and theme, by the way, are Rampart.
So, when storming a swamp with a Rampart, the following units might be defending it:
4 flyers - Golden Dragons, Pegasi (not necessarily upgraded), un-upgraded Wyverns, Angels.
1 ranged unit - upgraded Elves.
2 melee units - Unicorns and Centaurs (possibly upgraded).
Inside the castle, they will likely be greeted by the entire garrison.
If the defending hero has the Tower skill, it will be difficult. But if not, there will be a chance of "Centaur sacrifice."
Elven archers might try to block them, but it won't last long. However, fast flyers, using the tactical approach of wait-attack-retreat-wait, etc., can definitely solve the problem.

Орден Феникса – харизматический :) лидер