Location
	Leviathan can be drawn from Norg, during your fight in the Balamb Garden.

LEVIATHAN
	Elemental: Water
	Attack: Tsunami
	Level		HP		Atk. Power
	1		-		-
	17		1349		963
	20		1546		1075
	30		2206		1445
	40		2847		1815
	50		3550		2185
	60		4234		2555
	70		4926		2925
	80		5626		3295
	90		6334		3666
	100		7050		4036

Ability	AP	Opens		Ability	AP	Opens
SPR-J	Learned	None		SPR Bonus	100	None
Magic	Learned	None		Auto-Potion	150	None
GF	Learned	None		SUMMAG+10%	40	SUMMAG+20%
Draw	Learned	None		SUMMAG+20%	70	SUMMAG+30%
Item	Learned	None		SUMMAG+30%	140	None
MAG-J	50	ELEM-ATK-J		GFHP+10%	40	GFHP+20%
ELEM-ATK-J	160	None		GFHP+20%	70	GFHP+30%
ELEM-DEFx2	130	None		GFHP+30%	140	None
Recover	200	None		Boost	10	None
SPR+20%	60	SPR+40%		Supt Mag-RF	20	GF Rec Med-RF
SPR+40%	120	SPR Bonus		GF Rec Med-RF	30	None

Leviathan has the strongest water based attack in the entire game. Without a doubt, he will come in handy in the fights where the enemies are weak to water. Also his Recover Ability is something you will want to get right away.
You can also get the SUPT MAG-REF from Leviathan. This will allow you to refine items into support based spells. These are great defensive spells, that also junction well to your stats.