The Joiner of Cats is a rare Legendary Creature — Human Warrior card from Unknown Event (UNK), collector number RZ04h.
Whenever this creature attacks, look at the top six cards of your library. You may put a Cat creature card from among them onto the battlefield tapped and attacking. Put the rest of the cards on the bottom of your library in a random order. If you don't put a card onto the battlefield this way, create a token that's a tapped and attacking copy of Lurrus of the Dream-Den.