
Soulbond (You may pair this creature with another unpaired creature when either enters. They remain paired for as long as you control both of them.)
As long as Thundering Mightmare is paired with another creature, each of those creatures has "Whenever an opponent casts a spell, put a +1/+1 counter on this creature."
Thundering Mightmare has 3 printings, first in Crimson Vow Commander (2021). EDHREC ranks it #11,266 among Commander cards. It appears most in Skullbriar, the Walking Grave decks (2,693 on EDHREC).
Deck counts from EDHREC.
Cards that show up in the same decks on EDHREC.