My random ideas

These are my ideas for post moon lord content.

Luminite armour
After defeating the mech bosses again after the moon lord, there is a small chance (5%) of you getting "luminite souls" (ex. you get luminite souls of sight from the twins) and you need 10 of each of the souls and 15 luminite bars to craft luminite power fragments. Power fragments are used to craft Luminite armour. (helmet: 50 fragments, 70 defense, chest plate: 75 fragments, 90 defense, boots: 60 fragments, 80 defense. The set bonus is infinite flight.

last prism upgrade
to make the "lunar crystal" you need the last prism (of course) and 25 of those fragments mentioned above, as well as 35 luminite bars. This does 210 base damage. (this is the endgame magic weapon)