Hedron-Field Purists

The prevention effects don’t affect damage dealt directly to a planeswalker you control.

If a source would deal damage to multiple applicable recipients, the prevention effects apply to each of those recipients separately. For example, if Hedron-Field Purists is level 1 and you cast Earthquake (“Earthquake deals X damage to each creature without flying and each player”) with X equal to 3, that Earthquake will deal 2 damage to you, 2 damage to each creature without flying you control, 3 damage to each other player, and 3 damage to each creature without flying other players control.

Effects that modify a leveler’s power or toughness, such as the effects of Giant Growth or Glorious Anthem, will apply to it no matter when they started to take effect. The same is true for counters that change the creature’s power or toughness (such as +1/+1 counters) and effects that switch its power and toughness.