A few ideas inspired by Mysterious Cube.

Lucky Cube
3 Flux
1 UA
0 3/3 0 0 0
Each round Lucky Cube has 50% chance of generating 1 extra flux.

Cursed Cube
4 Flux
2 UA
1 4/4 0 0 0
Battle Ready
Can not battle back.
No enchantments can be cast within 2 spaces of Cursed Cube.

Nature Cube
1 UA + 3 Flux
OR
1 SYL + 1 flux
0 3/3 0 0 0
Controls any forests adjacent to it.
(2 Flux, Dim) Target Forest within 2 spaces of Cube becomes plains. Create a Sapling in space where forest was removed.

Chaotic Cube
2 UA + 4 Flux
OR
1 HoC + 4 Flux
0 3/3 1 0 0
Warps to a random valid hex each round. You cannot play a building that has 2 vision or greater adjacent to Chaotic Cube.