Genshin Impact
Millennial Pearl Seahorse, strategies, weak points, and achievements
Defeat the Nameless Lord of the Great Lake.
The Millennial Pearl Seahorse is a boss introduced in Fontaine in Version 4.1. To get to it, you have to enter an underwater cave, and when defeated, you can get the regular boss drops, especially Vajrada Amethysts (Electro) and Fontemer Unihorns.
As of Version 4.1, Neuvillette is the only character that requires Fontemer Unihorns as an ascension material.
Millennial Pearl Seahorse cave entrance Location
Cave entrance
Boss Location
Millennial Pearl Seahorse
Weak Point
The Millennial Pearl Seahorse does have a weak point. It is its Xenomare Pearl, which is infused with Electro, so you need to cause elemental reactions to destroy it, especially with Pyro, Cryo, or Dendro; if you use Hydro or Electro, nothing will happen to it, and if you use Geo or Anemo, it will do little effect.
After taking a certain amount of damage to the Pearl, the Seahorse will rise and place three Resonant Coral Orbs while also attacking you; these Resonant Coral Orbs have the same weaknesses as the Pearl; if you don't destroy them, the Pearl will regenerate some of its health.
Strategy
Most of the Seahorse's powerful attacks use Electro; it will do these attacks while its weak point is still intact. Destroying the weak point will cause it to do weaker versions of some of its attacks, causing only Physical damage.
Even when weakened, this boss does have a lot of Electro resistance, so avoid bringing any attacking Electro characters; if your strongest attacker is not Pyro, Cryo, or Dendro, make sure that you bring at least one of those elements to attack the Xenomare Pearl.
The Millennial Pearl Seahorse will regenerate its Xenomare Pearl only once per fight after it was destroyed, but it won't be as resistant the second time.
Achievements
If done right, you can get both achievements in the same battle.
Collezione di Sabbia
Break the Xenomare Pearl directly without destroying the Resonant Coral Orbs while the Millennial Pearl Seahorse is guiding Hoarthunder.
A Pyro, Cryo, or Dendro archer is recommended for this; when the Millenial Pearl Seahorse summons the Resonant Coral Orbs, instead of attacking those, attack the Seahorse to destroy the Xenomare Pearl.
Fulgura Frango
Defeat the Millennial Pearl Seahorse while it is attempting to re-construct a Xenomare Pearl.
It's pretty straightforward: after destroying the Xenomare Pearl, leave the boss with as little health as possible; if you can defeat it in one more attack, wait until the animation of the Millennial Pearl Seahorse getting itself covered in Electro starts and attack before it makes a new Xenomare Pearl.