Your search for "Gladiator Proving Ground PTDN-EN061" revealed the following:
Gladiator Proving Ground - PTDN-EN061 - Common - 1st Edition from Phantom Darkness 1st Edition, available at 401 Games Canada. Rarity: Common Card Text:Add 1 Level 4 or lower "Gladiator Beast" monster from your Deck to your hand.
Gladiator Proving Ground - PTDN-EN061 - Common - Unlimited from Phantom Darkness Unlimited, available at 401 Games Canada. Rarity: Common Card Text:Add 1 Level 4 or lower "Gladiator Beast" monster from your Deck to your hand.