Stonewright

Soulbond was the era's experiment in conditional, board-state-dependent abilities: pair two creatures while one enters, and a static ability switches on for both until you lose control of either. Most cards that carried it granted a defensive or evasive bonus. This one hands out a firebreathing ability, the kind of repeatable -for-+1/+0 pump that decks have leaned on since Shivan Dragon, but splits it across two bodies for the price of a single one-drop. The pairing is also the vulnerability: kill either creature and the pump evaporates on the survivor, so the value scales with how much red mana you can dump in a single combat step and how willing the opponent is to let two attackers connect. The pairing re-triggers, too, meaning a fresh creature entering can inherit the ability if the original partner has died, which keeps the engine alive longer than a one-time aura ever would. The real design weight sits in the math the controller runs mid-combat: every untapped red source becomes a damage decision spread across two threats, and the body it sits on is fragile enough that the ability has to win the race before removal catches up.