The Ultimate Leviathan

When The Ultimate Leviathan enters the battlefield, you may have it fight a creature you don't control. if it dies, you may have it fight another creature. When the Ultimate Leviathan leaves the battlefield, its owner may exile it and put 4 sea counters on it. Each turn, remove a sea counter from The Ultimate Leviathan. When there is 0, put it into play with haste and +10/+10.