Loki Laufeyson

A copy effect that grows into itself. The tap ability sets a ceiling tied to Loki's power, so the 2/1 body can only fork one- and two-mana spells until you invest in making him bigger; the copy is not a fixed reward but a moving one, gated by whatever the creature currently is. That is the tension the whole card runs on. The Power-up ability answers it in a single deliberate push: it lands two +1/+1 counters, but the oracle text limits you to activating it once, so the ceiling jumps from power two to power four in one payment and then stops. That constraint matters. It is not an escalating engine you keep feeding; it is one purchase that decides how big a spell Loki will ever be allowed to duplicate. The cost reduction for casting him the turn he arrives means that purchase is cheapest when he is most fragile, an incentive to commit the whole plan early rather than nurse a small body across turns. The copy trigger itself is patient in a useful way: you tap in advance and the fork waits for your next qualifying spell that turn, letting you set up before you know exactly what you want doubled. Building around him means a spell curve that fits under his single upgrade, so the deck's shape and the creature's one growth spurt have to be planned as one decision. The trickster framing is doing real mechanical work: a threat that cheats bigger spells only once you have paid the one time it costs to make him worth cheating.