Whenever it destroys a creature, it gets a +1/+1 counter
The deck features a huge number of powerful cat creates many of which have strong secondary abilities include anthem effects (Kaheera, Feline Sovereign, Jazal, Regal Caracal, King of the Pride), card draw (Beast Whisperer, Feral Prowler, Generous Stray), token producers (Cubwarden, Jolrael, Leonin Warleader, Pride Warden, Regal Caracal, Garrison Cat), removal (Stalking Leonin), artifact/enchantment destruction (Enlightened Ascetic, Felidar Cub), and many more
For those hunting down The One Ring, collector booster packs are priced at $42 USD each and $420 USD for a booster box containing 12 packs and a box topper card
It takes a concept (a species in danger of vanishing from the earth) and melds its mechanics to fit that idea (the creature literally has vanishing, but you can stop it if you take the right actions)
No other box toppers were shown in the most recent stream, but more variations on existing Magic cards were
