Asmodeus, Lord of the Lustful

Whenever a player casts a permanent, another
player may pay that permanent's mana cost
minus {1}. If they do, he/she takes control of that
permanent then loses life equal to the number of
permanent he/she controls that he/she doesn't
own.
At the beginning of each opponent's upkeep
Asmodeus, Lord of the Lustful deals damage to
that player for each permanent he/she controls
that he/she doesn't own.