Oblivion Walker

Collect 15 Daedric Artifacts - the game's biggest collect-all. Each comes from a Daedric Prince's quest (there are 15+ available across the base game, so you don't need literally every one, just 15). Work through the Daedric quests - Mehrunes' Razor, the Mace of Molag Bal, the Skull of Corruption, Azura's Star, the Ebony Blade, Volendrung, etc. A couple are mutually exclusive per playthrough, but there are more than enough to reach 15. The platinum-tier completionist grind; builds on Daedric Influence.