Battlecrest: Eterna Overlord Set

From BoardGameGeek:

The Eterna Overlord Set expansion contains 18 cards. It introduces a new 6-card map (playable in any game mode) and 12 cards for Eterna. This expansion creates a larger, multi-stage cooperative boss battle for 1–4 players, and was designed to be a much more streamlined experience than Imperator (quicker turns, less of a simulation). Eterna feels like a proper boss as well, unleashing round-altering effects, heavy hitting area-of-effect attacks, and structures that cover landmarks which must be destroyed to progress. Eterna Overlord set The Vault map set