Abilities » Royal Heal | Abilities » Sand Slammer
If you have Flygon with "Sand Slammer" active, but the opponent has Serperior with "Royal Heal" in play, which Ability goes first? The one that places damage or the one that heals damage?
In this situation, the player whose Pokemon are being affected gets to choose the order of when the abilities take place.
Source: TPCi Rules Team (2012-11-01)
Abilities » Royal Heal
Do I have to use Serperior's "Royal Heal" ability if I don't want to?
Royal Heal is not an optional ability. You must use this ability at some point in between turns.
Source: Black & White FAQ (2011-04-28), PUI Rules Team (2011-04-28)