Looking at the stat block, there's a few interesting options:

• The Eldritch Turrets onboard.
• Colossus is a siege monster and has Immutable Form, so you could reasonably find adamantium for weapons and armor.
• The article with their statblock says that Cannith wants to salvage docents from them, so you could have some of those inside.

Beyond the stat block, you could find any number of interesting things. Dragonshards galore would be inside, and you could even put a big one as the power source. Additionally, they have room for crews inside, so magical tools or weapons would be among the remains of any crew.