Eels are represented by a red-brown e
"The eel slips silently through the subterranean lake, waiting for unsuspecting prey to set foot in its dark waters."
They can easily dispatch a lower level adventurer who sets foot into the waters. Even levitating will not prevent them from attacking you. They also regenerate quickly. Be wary of bodies of water when you have low hp! If there is no land nearby, you may die if an eel repeatedly attacks. Attack staves are well spent on these.
"The eel moves quickly, moves erratically, never sleeps, is at home in water, cannot venture onto dry land and submerges"