Wow! I go to get some sleep and there are 20 more replies! You guys are amaizing!
Well, now onto my opinion..
I like the idea that Karzahni is staying imprisoned willingly, paranoid of what might happen if he escapes.
There is. The prison was built by Ekimu and Makuta. You know, prisons are built to contain the prisoners, not let them die. If it was their brother held up in there, they would make sure he stays alive.
There has to be some sort of defense mechanism if anything happened, so, when the island sank, and all the prisoners would be drowned, a mutagen would be released that helped them live underwater, but, in turn, changing them into monsters.
How about that?
Either way, thanks for the activity you're giving to this thread!