Time traps! NOT RIFTS, as you might have guessed by the abilities on Bahamut's O companions. The initial stages have a few time traps near the corners, while the final stage has time traps completely filling the 2nd and 3rd rows from the top and bottom. It's basically impossible to move without a time trap ward character. Leviathan has all the usual stuff, ice barrier, maelstrom, icicle, re-summoning minions that confuse and lay sea mines. Leviathan has a tendency to push people into the mines and kill them, which can be annoying. Beat it with Piz'fer Λ, Lewto Λ, Daiana Λ, A'misandra Λ, Gegonago Λ, Shin'en Λ, all with Ice Shield companions. Yay for 0 damage icicle. I might make a movie of the final stage, but it's kind of long and boring.