Based on the information I see above:
- Q: Does Icicle roll for Slick Ice Spray on a figure that chooses not to move this turn?
- A: No. In this case "begins its movement" refers to when a figure attempts to move, not the turn order of movement.
Can I get a Hero to confirm this, it seems wrong to me. Although thematically it seems right (if you do not move, you will not fall), I would actually think it would be like a power that states "before moving" where it refers to the order actions are done in a turn.