I really love the design of the Swarms movement. A pitfall that I feel some of the other Root factions fall into is that other than via battling they don't involve other players much. The swarms movement allowing players to reveal cards to redirect the swarm is fantastic, albeit in this from it is a bit wordy and could do with some simplification.
I also love factions that heavily affect how the board needs to be looked at. The Arid markers being left behind by the swarm very nicely gives the feeling of an encroaching inexhaustible tide.
Bravo!