Mordred's Hideout

In Astro Knights Island
Mordred's hideout is where Mordred escaped imprisonment in the dungeon and continued his work, but when the king and queen found out where he was hiding, Mordred escaped into space using a spacecraft he had not yet finished.

In Super Villain Island
Mordred's hideout is apparently destroyed in the Binary Bard's mind, if you click on a torn portrait of Mordred, your poptropican will say: "I'm guessing this is when Mordred started to fall into madness.".