What's the Legendary Crystal from DUNGEONS DAY

Bassanio

There's a Legendary crystal in the Additional Milestone Reward.
Dose anyone knows the details of legendary crystal.

Nickname207

Legendary crystal gives 4* as minimum and a chance at 5*. I read somewhere the drop rates are 80% - 20%, respectively

Solswerd

Yep, that is the one. Those drop rates are also correct.
But keep in mind that last milestone with the legendary crystal only shows up if you are above a certain level of prestige.