in its mana cost, X is 0.Meren of Clan Nel Toth turns creature deaths into an experience total that survives her removal. Whenever another creature you control dies, you gain an experience counter. At your end step, she targets a creature card in your graveyard: a low enough mana value returns it directly to the battlefield, while a card above your experience count goes to your hand.
That means the engine can start before the experience total becomes large. Sakura-Tribe Elder can search for a land, add experience when sacrificed, and become an inexpensive return target. Spore Frog can provide a defensive recurring effect, while creatures with entry abilities supply removal or cards as the available mana-value range increases.
You retain experience counters as the player even if Meren leaves the battlefield. Removing her interrupts the end-step engine, but recasting her can resume with the progress already earned. Tokens can help generate experience when they die, although they cannot later be returned as creature cards from the graveyard.
Sacrifice outlets control timing and make sure the deck has a useful target before the end step begins. Graveyard interaction remains a direct way for opponents to disrupt the chosen return, so avoid making every plan depend on one exposed creature card. Meren rewards a curve of useful creatures rather than only expensive reanimation targets: the smaller creatures build experience and resources, then the larger returns become available as a natural consequence of playing the deck.
