Whirpool/Full Speed Challenge Spot: A Father’s Thoughts and Mysterious Savior
To be fair, this island doesn’t have an actual name.
It’s the one that’s west of Twinning Isle and north of Broken Isle. You’ll know you’re at the correct location because it’s also the spot where you can start Act II’s “Whirlpool off to Starboard, Full Speed Ahead” challenge.
There’s also a chest here that’s shielded. You’ll be able to unlock it as you progress further.
There are three towering rock formations here (west, north, and east). I suggest climbing the one to the east since that has stairs and Anemo stones that can create wind currents.
Just whack the enemies that you spot and try not to get tossed off the edge (i.e., hilichurl bombs or exploding slimes). Once you reach the top of the eastern rock formation, defeat the hilichurls (especially the samachurl/shaman) to weaken the forcefield of the main chest.
Follow the rope bridge as it leads to the northern rock formation. On one of the ledges, you’ll find “A Father’s Thoughts.” Keep at it until you reach the top and kill the hostiles there. This will break down the forcefield again.
Finally, make your way to the western rock formation. There’s a hilichurl prison camp here and the “Mysterious Savior” Echoing Conch can be found inside one of the cages.
After beating the mobs, the shield of the main chest down at the beach should dissipate. You can head back down to fight a Stonehide Lawachurl. Once you’ve eliminated it, open the chest to complete this secret sidequest. You’ll also receive 50x primogems for your trouble.
