Loop Hero

This unlocks for defeating the Lich, the Chapter 1 boss, 3 times. It is important to note that the boss will get stronger the more loops you complete in an expedition. So you want to spawn the boss in (by placing enough tiles) early enough that it isn't too strong, but late enough that you can unlock gear and gain stats. You'll need to start 3 separate expeditions to complete this.

Stats you should focus on for this fight are:
Max HP
Regeneration
Evasion
(Other stats like Vampirism are great to have, but don't prioritize them over the stats listed above)

Additionally, the boss spawns in on your camp tile and will spawn Temple tiles in any empty space adjacent to your camp. These Temple Tiles increase the boss' stats. Throughout your expedition, you should try to fill all of these empty tiles to stop temples from spawning. You can also use oblivion cards to destroy the temple tiles.

Below is a video that also explains the strategy in more detail!