It's a 3-D game of tower defense... it's Aetherspire!

About Aetherspire, from BoardGameGeek:

The realm of Elementis, once a harmonious balance of earth, air, fire, and water, is now under siege. Elemental Aetherfiends have dispatched waves of invaders to drain our aethercore, the realm's lifeblood, causing chaos to reign. You and your companions must build powerful elemental spires to lure away and defeat these invaders. As each spire grows stronger, it will unleash a devastating resurgence against the Aetherfiends. Can you restore balance before it's too late? Aetherspire is a cooperative 3D tile placement and tower defense game for 1-4 players. You and your companions will take on the role of Elementis heroes, working together to mold elemental power into four spires, one of each element: earth, air, fire, and water. A spire is a set of four floor tiles, one on top of another, all of the same element. Each time you complete a spire, that element's aether fiend is defeated. Once all four aether fiends have been defeated, the heroes share in glorious victory, having restored balance to the realm of Elementis! However, if the precious aethercore is depleted, or if you take too long to defeat the aether fiends, then the heroes lose the game, and chaos will overtake your world! -description from the publisher