Thundering Mightmare
Soulbond usually hands out a static keyword: flying, deathtouch, lifelink, the kind of shared upgrade that reads well in a bonded-pairs draft environment. This one shares a growth engine instead, and it points at the wrong side of the table. Whenever an opponent casts a spell, both paired creatures each gain a counter, which flips the usual soulbond math: the reward scales with how active your opponents are rather than with anything you do. In a two-player game that clock is slow, but the counter trigger fires on every spell an opponent casts across a full pod, so the more players and the more spells hitting the stack, the faster both bonded bodies balloon. It is a multiplayer-native design wearing a keyword built for the two-player margins soulbond first appeared in, and the disconnect is the whole point: a mechanic tuned for symmetrical duels repurposed as a punish-the-table growth incentive. The pairing choice matters too, since the counters stick to whatever creature you bond, letting you graft a snowballing threat onto something already built to carry counters or convert them. Nothing about the 3/3 body or the five-mana price makes it a keystone; the interest is structural, a small example of an old two-player keyword being asked to do work in a format its printing predates.
