There are two Lleviathans you can meet in the game, one is the Fygg-changed form of Dylan Jones, the other is a real Lleviathan that lives around for a long time. The first is a boss that must be beaten to continue the main story. The other is available after the game is beaten, met through a quest given by Jona Jones.
Lleviathan appears as an A-rank monster of the Nature family as part of the limited Dragon Quest IX event. He will join the party in Chapter 4, Episode 1 of the event quests entitled Lt Goreham-Hogg and he stars in his own Battle Road. Lleviathan can be fully awakened by completing the Fantastical Fish Hunt of "Move out! Exploration Team Majellan" at any difficulty.
Sea God's Rage Potency +5% / Stats Up Rare Damage Barrier: Rarely grants a barrier that reduces damage by 15% for 3 turns at action start.
Fourth
Fifth
Crack Res +25 / Stats Up
Sea God's Rage Potency +5% / Stats Up Porth Llaffan Guardian: Raises move and martial potency/effects for 1 turn at action start on even turns until turn 10.
Leader Perks
First
Lowers enemy Martial Res by 5% in a 5x5 square around him.
The Japanese name of Lleviathan is ぬしさま, where ぬし(nushi) means "the Lord" or "god" and さま(sama) is a suffix used for courteous addressing. This is probably because Lleviathan is worshiped by the inhabitants of Porth Llaffan as the God of Sea.
The double L in its name is the Welsh Ll sound, owing to the Welsh dialect found in Porth Llaffan.
Lleviathan is a reference to the Leviathan, a sea monster mentioned in the Old Testament of the Bible. It appears as a metaphor in the Book of Job and as the creature that swallows up Jonah in the titular book, which is played out when Lleviathan swallows Jona before the Hero engages the creature in battle.