Filigree Crawler

A four-mana 2/2 is undersized by any reasonable curve, and the death trigger is what pays for the gap: trade the Crawler away or feed it to a sacrifice effect, and you keep a 1/1 flier holding the ground you just spent. That two-bodies-for-one structure is the card's whole reason to exist. The value is back-loaded, not front-loaded: the Insect itself blocks and dies cheaply, but the Thopter it leaves behind is the part that actually does work in an attrition game. It rewards being an obstacle rather than a threat, which inverts the usual artifact-creature math where you want the body to stick. In the wider artifact ecosystem it reads as deliberate sacrifice fodder: a creature you want to lose, because losing it converts a clunky ground blocker into evasive air defense and an extra artifact for whatever cares about artifact count. The catch is that the conversion only fires once and only on death, so it asks to be paired with effects that want to throw it away, not protect it.