Kelvelos at a glance
WhereThe Forest of Wisdom, near Ellinia
Who can fightTamers only
Level30
Respawn2 hours after it falls
DropKelvelos's Heartjelly (always)

Kelvelos is a huge humming slime that only a Tamer's partners can fight: ordinary attacks, spells and arrows do nothing to it, and it can never be caught.

Rowen's quest

The Slime That Hums from Rowen the Fairy in Ellinia (level 25, adventurer classes): bring her one Kelvelos's Heartjelly. Since only a Tamer can defeat Kelvelos, an adventurer goes with a Tamer and picks up the Heartjelly it leaves. Reward: 60,000 EXP, 15,000 Vesos and 10 Elixirs.