Lost Ruins of Arnak: Expedition Leaders

The six leaders completely change how you approach the base game, especially the captain who lets you manipulate your deck differently each round. My group has played it four times now and nobody wants to go back to the vanilla setup.

Picked this up after wearing out the base game, and the leader asymmetry totally changes how you plan your turns. Playing the explorer who gets extra movement made the temple race feel completely different from my usual strategy.

The leader asymmetry completely changed how my group plays, since each of the six has genuinely different abilities and skill trees instead of just a stat swap. My usual strategy fell apart when a friend picked a leader that let her rush the temple track, and I loved that.