Castles are larger than Keeps, but not quite as large as Fortresses. Retaliations sent by Castles can consist of up to 10 or more more units. Clicking on a Castle returns the message, "This is a high level military structure, beware." Castles require a base Hate of 500 before they will launch reprisal attacks.
Occupants: 20-40 Elves, levels 50-350 (chance of encountering a level 50-200 Paladin).
Commonly referred to as an "F2" (Fortress Tier 2) Settlement.