>walk across the dead sea monster. Open door that is across river using handle.
The interesting thing about parasites, is that they're perfectly adapted to making good use of their hosts. The sea serpent bends at an unnatural angle, and spits burning acid upon you. Your cerebrospinal fluids are quickly drained thereafter.
There is a river, completely still. On the opposite shore, there is a marble door. The ground appears to shift when you look away from it. The door behind you seems to have disappeared.
>continue.Stand at a (assumed) safe distance and examine sea monster.
It has fallen over. Upon careful examination, you see that its skin and flesh are translucent. There is a dark green fluid flowing from its head to the rest of its body.