Select 2 cards from the Graveyard(s), and shuffle them into their owner's Deck(s). After activation, remove this card from play instead of sending it to the Graveyard. You can only activate 1 "Pot of Benevolence" per turn.
Aside from Gravedigger, use Disappear trap card. Because sometimes, in a 20 card deck, you can't seem to draw this in first 4 turns (bad starting hand)
I use this in my Cerberus deck against those pesky card-munching fiends like Tea with her Skelengels or Yugi Muto Lv 40 with his spell after spell after spell after spell. Also, it's helpful for replenishing the opponent's deck after using multiple Abyssal Designators. The N-rarity makes this card amazing - I (likely) don't have to spend thousands of gems to get more than one copy! Do remember though, this doesn't go into the graveyard but banishes itself after usage! No infinite loop for you (yet?)!!
If I chain Twister to it, the two cards selected go back into their respective decks but the Pot of Benevolence itself also goes to the graveyard! I smell an infinite loop here! As long as you remember only one activation of Pot of Benevolence is allowed per turn.