Their Number Is Legion

The graveyard permission reads like a contradiction until you see it as insurance. A cast that resolves exiles the card, so the recursion never fires off its own resolution: the "cast from graveyard" line only goes live when something else buries the spell first, a mill effect, a discard, a counter. That is the point. Answer this the usual way and you have not answered it. Counter it and it lands in the yard, where it can be cast again for the same ; strip it to hand disruption and you have merely relocated it to a zone it is happy to be cast from. The cost never drops, so the second cast is a reprieve rather than a discount, but a reprieve is more than most army-in-a-can X-spells offer. The lifegain rider is where the payload compounds: the Necron Warrior tokens are themselves artifacts, so the number it counts already includes the bodies it just made, and a wide swarm feeds the artifact-matters shell (cost reducers, sacrifice fodder, enters-triggers) that wants those bodies on the table anyway. The four black pips and the tapped arrival keep it a deliberate mid-game commitment rather than a cheap flood: you pay the full black-hungry price for a swing that lands a turn late. What the card really trades on is durability, an X-spell that keeps offering itself back after the answers have been spent.