EastScape Wikibuilt from the game itself

Raw Leviathan eel

Where to find it: The Frozen Reach (The deep pool, Fishing 99; Concentrated leviathan eel spot, Fishing 99).

“A slab of something enormous from the bottom of the Frozen Reach's deep pool. It's still twitching. It takes a glacier rod (Smithing 95).”

Gathered from

WhatWhereSkillLevel
The deep poolThe Frozen ReachFishing99
Concentrated leviathan eel spotThe Frozen ReachFishing99

Used to make

MakesSkillLevelAlso needs
Leviathan steakCooking99—
The Leviathan platterCooking992 Frostbloom
Smoked leviathan eelCooking993 Charcoal