Infinite Power
Very rare2.5%ObjectiveOptional
Obtain the most powerful weapon.
The 'most powerful weapon' means an Infinity weapon: take a Galaxy weapon and forge it with three Galaxy Souls at the Volcano Forge on Ginger Island (plus the cinder shard cost).
The chain: get a Prismatic Shard, carry it to the Three Pillars in the Calico Desert to receive the Galaxy Sword (or buy the dagger/hammer variants from the Adventurer's Guild afterwards), then earn Galaxy Souls - 40 Qi Gems each at Qi's Walnut Room shop, or drops from Qi's combat special orders. Forge all three in and the Infinity weapon pops it. Expensive, late-game, and genuinely worth having for 818922349.