Brad, Forgetter of Names

When this creature enters the field,
pay {x} mana to forget your opponents' names.
For each name forgotten, gain (in this order)
+5/+5, vigilant, and indestructible. If you say
one of the forgotten names at any point during
the game, you lose.
"Hey man, you gonna play Arceus later or what?"
-Brad, Forgetter of Names