Luminite Bar

Luminite Bars are a type of bar used to craft all four sets of endgame armor and tools as well as other endgame items. The only way to obtain it is to craft it from Luminite, which is dropped from the Moon Lord, at an Lead Anvil. Each time the Moon Lord is killed, it drops enough Luminite for 17-25 bars ( 21-27 in Expert/Master mode).

Crafting all items (excluding me) requires a total of 317 Luminite Bars (1,268 Luminite; requires defeating the Moon Lord 15–19 / 12–15  times). Crafting all items pertaining to one type of Lunar Fragment (i.e., armor, wings, pickaxe, and hamaxe) requires 68 Luminite Bars (272 Luminite) in addition to 85 of the Lunar Fragment; this requires defeating the Moon Lord only 3 / 2-3  times.

Trivia

 * Luminite Bars are the most profitable bars in the game, selling for each.
 * However, the Void Monolith, made from 25 Luminite (just over 6 bars worth), sells for.
 * Luminite Bars are the only bar that can stack past 99, up to 999.