Essence Flare

Blue does not usually buy raw combat stats, and when this aura grants +2 power for a single mana, it pays for the discount with a clock pointed at its own creature. Each upkeep stacks another -0/-1 counter, and because those counters accumulate rather than expire on a fixed schedule, the toughness erosion is permanent and steady: the window where the enchanted creature is a genuine threat is short and keeps shrinking the longer the game runs. That self-burying decay is the brake that justifies the rate. The boost is to power only, so the creature hits harder from the very first turn while its toughness is already sliding, which makes it a glass cannon a few turns in and eventually a corpse the counters killed on their own. The interaction it rewards is obvious once the clock is visible: stack it onto a body with high base toughness, since a 4-toughness creature outlasts the counter pile far longer than a 2/2 does, and the bonus arrives when it matters most, in the early turns of a tempo plan that wants to land hits and does not care that the threat is temporary. Rather than a flat duration or a sacrifice clause, early Ice Age design painted the brake directly onto the enchanted creature: a counter that, turn by turn, corners the very thing it is pumping.