Deluge Virtuoso

The tempo half arrives first: an enters-the-battlefield tap-plus-stun that soft-locks an opposing blocker or attacker for a turn, buying the exact window a proactive spells deck wants. That alone would make a serviceable body. The Opus clause is where the ambition lives. Rather than gating on spell count or a single trigger per turn, it pays out every time you cast an instant or sorcery, and it scales: the standard bump is +1/+1, but a spell that consumed five or more mana turns the payout into +2/+2 for the turn. That five-mana threshold is the design's cleverest hinge, because it rewards not just casting spells but casting big ones, folding X-spells, kicker payments, and expensive finishers into the same growth engine that cheap cantrips feed. A 2/2 does not threaten much, but a spellslinger board can stack multiple triggers in a turn and swing for a total that has nothing to do with the printed stats. The stun counter is worth dwelling on: it is a strictly tougher lock than a plain tap, since the affected permanent burns its next untap step removing the counter instead of straightening up. Pair the counter's window with a creature that only gets dangerous once you start casting, and you have a two-part clock: neutralize their defense on entry, then grow past it as the spells resolve.