Mordenkainen

The plus ability is the honest one: it draws two and bottoms a card, netting one while filtering, so it climbs loyalty and refills without the usual walker tension between defending and advancing. That filtering pulls double duty, because the whole planeswalker is built to reward a fat hand. The minus-two spits out a token whose power and toughness scale to twice the cards you are holding, turning stored resources into a body you can deploy at will: control decks that sit on cards suddenly own a lethal threat made entirely of what they have not spent. And the ultimate is the payoff for a deck sitting on a stocked library, swapping hand for library and handing you an emblem that removes the maximum hand size, so nothing you swapped into gets discarded on the way to the win. What ties the three modes together is that they all reward hoarded cards, whether in hand or library, which is unusual for a walker whose abilities more often pull against each other. The archmage framing supplies a famous name, but the mechanical identity is a hoarder's engine: it asks you to bank cards rather than spend them, then cashes the stockpile three separate ways, once for loyalty, once for a board, once for the win.