Sky and Luna, Watchdogs

Your deck may contain an additional copy of
Sky and Luna, Watchdogs.
Whenever a creature enters under an opponent's control, that player loses 1 life and you gain 1 life.
As long as you control exactly two permanents named Sky and Luna, Watchdogs, the "Legend" rule doesn't apply to them.
Each other creature you control named Sky and Luna, Watchdogs gets +3/+2.