The giant egg in the Dragoncave must be dug into and entered in order to summon the boss. When the player is about a third of the way into the egg, the boss will spawn in its center and emerge. The Suomuhauki itself behaves identically to a Jättimato with the notable addition of much better air control (flight). It will otherwise fly about in the same manner & pattern as a worm, deleting terrain as it goes, trying to collide with the player in order to cause practically instant death via heavy bite damage with its jaws (1,900 - 2,000 damage per second). The bite damage is not actually melee damage, even though Melee Immunity blocks it. In addition to its melee charges it also regularly spews 20 small fireballs at a fast rate, making up for its measly 2 damage, and regularly shoots 6 slow green orb projectiles in a hexagon pattern from the eye on its tail. It is quite durable and can take a lot of damage before dying, but slicing and explosion damage seem to work very well against it. If you have the Melee Immunity perk the only threat it poses to you will be the fire projectiles (2 damage) and the tail-projectiles (19 damage). The Projectile Repulsion Shield makes this boss significantly easier by effectively nullifying the slow tail projectiles and minimizing the chance that the flame breath attack will land.