Mephisto, Haunter of Dreams

Deathtouch
When Mephisto enters the Battlefield choose one creature and put 5 Pact Tokens on it.
A creature gains +1/+1 for every pact Token.
If a creature with at least 1 Pact Token on it
dies its controller looses 10 life.
When Mephisto is destroyed shuffle it back into your library.