It wasn’t until I started trying to come up with some powers that I truly realised just how much potential Iceman really has.
I didn’t end up devising a whole set of convoluted and tricky new abilities. Essentially, there’s nothing we haven’t already seen before in these powers in terms of game mechanics - just presented in a new way.

Avalanche (Active Blue, 12 AP)
Destroy up to 5 Blue tiles, dealing X damage to each enemy per tile. Does not generate AP.
Rank 2: Destroy up to 7 Blue tiles.
Rank 3: Also stun the enemy team for 1 turn.
Rank 4: Also deal an additional X damage for any special Blue tile destroyed.
Rank 5: Destroy all Blue tiles.
Max Level: Deals 185 damage per tile, and an additional 185 for each special tile destroyed.
This is a huge AoE attack to rain destruction on the enemy team. I think at Rank 3 you’re probably paying a little too much for what you get, but Rank 5 might even be undercosted if there’s enough blue special tiles on the board. Of course you’ve also just eliminated Blue off the board, so you’re probably not going to be chain casting with any great regularity.

Icewall (Active Yellow, 10 AP)
Create a random blue protect tile (low strength).
Rank 2: Increase strength.
Rank 3: Create 2 random blue protect tiles.
Rank 4: Increase strength.
Rank 5: Create 2 random blue protect tiles and 2 random locked blue protect tiles.
This is a little sneaky, and I’m working on the assumption that Avalanche will still target the locked tiles - unlocking them, but not actually destroying them. As such, this ability protects your team but also fuels a more powerful Avalanche.

The Iceman Cometh (Passive Black)
At the start of each turn, if there are 6 or less blue tiles on the board, add a random blue basic tile.
Otherwise, if there are more than 6 blue tiles, convert a random blue basic tile to an attack tile of strength X.
Rank 2: Add a blue basic tile when there are 7 or less blue tiles.
Rank 3: Add a blue basic tile when there are 8 or less blue tiles.
Rank 4: Add two blue basic tiles when there are 10 or less blue tiles.
Rank 5: Add two blue basic tiles when there are 10 or less blue tiles. Otherwise convert two attack tiles.
The power represents a lot of different things. It’s the unavoidable eventuality of entropy, in the end heat will die out and only the cold will remain. It’s the potential power of a glacier, slow but sure. It’s the kind of gathering storm which makes Iceman powerful. With very little at his disposal, he will draw the very moisture out of the air, but when he’s truly in his element, he can be devastating. Also, I gave it a cool name.
The blue generation seemed like a straight forward enough concept, but I needed 5 ranks and I thought that continual blue generation could maybe end up being OP. So there’s a tipping point, when there’s enough water/snow/ice/whatever around, Bobby doesn’t need to be making more of it and the ice storm kicks in. I wanted the choice between Ranks 3, 4, and 5 to be a choice of how long a player wanted to go before the attack tiles start. At Rank 3, the storm starts with 9 blue tiles. That’s the expected average, so it should kick in often enough. Ranks 4 and 5 have a higher threshold, but fill up faster. Not sure on the damage value for each attack tile, maybe 70. That’s less than the damage you’d deal by matching the tile, but keeping more Blue Special tiles in play feeds Avalanche’s strength.