When this creature enters,
clashTo clash, a player reveals the top card of their library. That player may then put that card on the bottom of their library.
“Clash with an opponent” means “Choose an opponent. You and that opponent each clash.”
Each clashing player reveals the top card of their library at the same time. Then those players decide in APNAP order (see rule 101.4) where to put those cards, then those cards move at the same time.
A player wins a clash if that player revealed a card with a higher mana value than all other cards revealed in that clash. (CR 701.30) with an opponent. If you win, put a +1/+1
counterTo counter a spell or ability is to cancel it: remove it from the stack without resolving it. A counter on an object or player is instead a marker that changes characteristics or interacts with rules or abilities; for example, a +1/+1 counter modifies a creature’s power and toughness. (CR 701.6; 122.1) on this creature. (Each clashing player reveals the top card of their library, then puts that card on their choice of the top or bottom. A player wins if their card had a greater mana value.)