Arcbound Overseer

Most modular creatures grow only themselves and bequeath their counters once, on death. This one runs the math in reverse: every one of your upkeeps it manufactures another +1/+1 counter on every modular creature you control, so the counter total only ever climbs while the engine survives. Eight mana buys a body that arrives carrying six counters of its own and turns a board of disposable robots into a snowball that no single trade can unwind. When one modular creature falls, its counters relocate onto another artifact creature, and the team keeps inheriting whatever it leaves behind. The Frogmite-and-Arcbound shell built around it never minded that the Overseer itself is slow; it minded that one death feeds the next threat instead of resetting the board. This is the payoff at the top of that curve, the card the cheaper modular creatures were quietly building toward, and the reason a deck full of expendable golems could afford to trade off in combat all day. The eight-mana price is the honest cost of an effect that compounds: by the time it untaps once, the arithmetic is already lopsided. Its printed 0/0 is a technicality the moment it resolves, because modular hands it six counters before its first upkeep and the spread clause keeps adding more on each of your upkeeps. That is not a small body; it is a tax on patience, levied against anyone who let the game reach the back half.