Lobelia, Defender of Bag End

Theft here is not the value engine it looks like at first count: Lobelia strips the top card of every opponent's library on entry, but those cards sit exiled face down and stay stranded there unless you feed the second ability. That fork is what disciplines the card. The artifact-sacrifice cost is the meter you pay to convert the stockpile, and every activation forces the same choice: spend the tap and the artifact to play one of the stolen cards for free, or convert the whole apparatus into a Gray Merchant style drain, two life each way. Lobelia refuses to do both in the same activation, and refuses to do either without an artifact to burn, so the payload is only as large as your token generation and your willingness to trade permanents for tempo. It is a rare piece of black exile-theft that ties its payoff to an artifact economy rather than to a graveyard or a sacrifice loop, which pulls it toward Treasure decks and artifact-fodder shells more naturally than toward pure aristocrats. Because the entry trigger tells you exactly what you took (you look before you exile), the free-play mode is never a blind gamble: you already know whether a stolen card is worth a whole activation. The drain mode is the reliable floor for the turns when the top of an opponent's library offered nothing you wanted, so no activation is wasted even when the theft comes up empty.