Rod of Absorption

A group-wide replacement effect wired into a payoff, which is a rarer construction than it looks. The first ability does not touch your spells or your graveyard specifically: every instant and sorcery cast by any player at the table gets exiled under the Rod as it resolves, so the artifact quietly builds a shared archive out of the whole game's spell activity. That framing is the interesting part, because the second ability lets only its controller mine that archive, casting freely from among the exiled cards up to a chosen mana value. The friction is deliberate: the X is a mana investment paid on top of the sacrifice, so raiding a fat exile pile costs real mana, and the artifact destroys itself in the process, converting a slowly accumulated resource into a single explosive turn. It also rewards patience over deckbuilding tightness, since the more spells resolve while the Rod sits on the battlefield (yours and theirs), the deeper the pool grows. Note what it does not do: there is no snapshot, no timing trick, no way to cast a spell that has not already resolved once. It reruns the game's spellcasting history on your terms, and the value of the payoff is set entirely by how long you let the table fill the reservoir before you cash it in.