Crimson Desert: Sanctum of Absolution

Game8 calls this an optional sanctum, not a main-story gate. It sits in southwest Hernand between the Witchwoods and Sunset Valley. The fight inside is Antumbra's Sword. After that you collect reactor cube pieces and work a dial. The prize is the Core of Absolution, which the same page says upgrades the Kuku Pot.

Other sanctums in the table also mention an Abyss Artifact. This one is different because the named prize is the core, and that is why it has its own page. I only have Game8 for the cube steps, so the status is one source. Do not confuse the sword here with the Darkbringer weapon, which is a separate Ator drop.