Opaline Sliver

Most Slivers hand the tribe a body part: a keyword, a stat boost, a tap ability that the whole colony shares. This one distributes a punishment clause instead. Once it resolves, every Sliver you control becomes a trap: targeting one with a removal spell hands its controller a card the moment the spell is cast, and the same toll attaches to bounce, combat tricks, and targeted aura plays. The design weaponizes the tribe's structural weakness, which is that Slivers are interchangeable and individually expendable, by making any attempt to pick one off cost a card. The clause is narrow in a way worth noting: it keys on a Sliver becoming the target of an opposing spell, so it rewards single-target interaction specifically. A sweeper that destroys all creatures without targeting slides past it untouched, which means the opponent's best out against the swarm is also its best out against the engine. The trigger ignores whose turn it is, so an instant-speed answer cast during your attack step refuels you exactly as cleanly as one cast on the opponent's turn. That puts the tactical squeeze on the opponent: leave the swarm alone and it widens, pick at it and they hand you cards. It belongs to the smaller set of tribal lords that defend rather than amplify, the colony's insurance policy rather than its accelerant, and its value scales with the width of the board rather than its height.