Tidal fortress

Opens from rank B.

Rank	Monsters	Bosses
B	Ningyo, Sazae-oni, Heikegani, Isonade, Umikozō	Ryūjin, the Sea Dragon King, Umibōzu, Giant of the Black Sea
A	Ningyo, Sazae-oni, Heikegani, Isonade, Umikozō	Ryūjin, the Sea Dragon King, Umibōzu, Giant of the Black Sea
S	Ningyo, Sazae-oni, Heikegani, Isonade, Umikozō	Ryūjin, the Sea Dragon King, Umibōzu, Giant of the Black Sea

Half of these gates hold the variant's second boss, Umibōzu, Giant of the Black Sea, instead of the usual one.

Monsters

	Monster	Rank	Material
	Ningyo	Mob	Ningyo Scale
	Sazae-oni	Mob	Sazae-oni Shell
	Heikegani	Mob	Heikegani Claw
	Isonade	Mob	Isonade Tooth
	Umikozō	Mob	Umikozō Ink
	Ryūjin, the Sea Dragon King	Boss	Pearl of the Tides
	Umibōzu, Giant of the Black Sea	Boss	Umibōzu's Ladle

Crafted from its materials

Ningyo Scale Mail · Shell Helm · Bow of the Pearl · Ladle Amulet

Mining

Every gate grows crystal veins (see Mining).