Ghostly Pilferer

The second ability is the tell about who this was built to punish: a whole class of decks that generate advantage by casting from outside the hand. Flashback graveyards, adventure exiles, foretell and cascade and impulse-draw shells all bleed a card to you every time they do their thing, and the Pilferer sits there as a two-drop tax collector on that entire style of play. It is a hatebear wearing an evasive body rather than a static ability, which is the more interesting version of the idea: it demands nothing be disruptive to be relevant, it just quietly refuses to stop drawing you cards while the opponent enables it. The other two lines keep it from being dead when nobody is casting from the yard. The untap trigger turns each turn into a soft repeatable cantrip if you have the mana to spare, and discarding a card to make it unblockable both feeds the untap loop's appetite and lets a 2/1 keep connecting for the two damage that adds up. The connective tissue is that everything wants it tapped down and swinging: attack, become unblockable, deal two, untap next turn, pay to draw. A Spirit Rogue that would rather grind you out with card advantage than race you, and that gets meaner the more graveyard-and-exile machinery it is pointed at.