Literally use The Creator to both discard and Special Summon Slifer. Discard Slifer as a cost to summon another monster in your Graveyard, then next turn you can discard another card to Special Summon Slifer from your Graveyard. If Slifer is SS'ed its goes back to the GY in the end phase, so just discard another card on your next turn to summon it again.
I had him in my LAST pack of the 200 in Electric Overload. That's on purpose from the Game ''creators''.. annoyed af