Burst of Energy

Untapping a permanent at instant speed for a single white mana is an effect that exists almost entirely to enable something else: the untap is only ever as good as the thing it untaps, and the spell asks you to bring the payoff yourself. Untap a creature with a tap ability and you have doubled its output for a turn; untap a land that taps for two or more, or a high-yield artifact-mana source, and you have effectively cast a one-shot ritual (untapping a basic land nets nothing, since the spell already cost the mana that land replaces). That last category, the big mana rocks and tap-to-do-something artifacts of late-90s Constructed, is where the card spent its design life. The trouble is structural: white has historically lacked strong tap-engines in its own color, so the spell rarely had a home that justified the slot. What you get is combo infrastructure with no native combo, a building block waiting for a payoff that white seldom supplied. Stripped of an engine, it falls back to small fair uses: keep an attacker back to ambush a creature, free a permanent from a tapper, squeeze one more activation out of something before the turn ends. The design is honest about its narrowness. The untap is unconditional, instant-speed, and a single white mana; the only constraint is that the card does no work on its own.