Of Land and Sea Part 9:
... lol, was busy and forgot to take a pic...
but you have to upgrade Tidegate to Lv6 and "summon" Heksa.
Of Land and Sea Part 10:
Fight Heksa ( 99 energy, and only few hit with 2 hearts, so you need nearly 90 hits to ****. and very rare energy back )
For me she Drops 4 Cursed Reef and other Stuff.
Of Land and Sea Part 11:
Clear a Cursed Reef 0/1 go
Gather Cursed Coral 0/3 go - skip 60gems ( drops from Cursed Reef - rare )
Forge a Coral Sword 0/2 forge - skip 160gems
Meet Thurston at the Tidegate Lv8 0/1 summon
Coral Sword ( Magic Forge ): 3 Cursed Coral, 2 Marmosea Venom, 1 Black Pearl - 8h
Upgrade Tidegate Lv7 ( 6 Sea Witch's Calling, 50 Jellyfin Jelly, 2 Coral Sword, 8 Witch's Scent )