Leyline of Lightning

The Leyline cycle's signature trick is that it converts a four-drop into a turn-zero board state, and this is the one built to punish a developing opponent rather than protect you from theirs. Free deployment from the opening hand turns a sorcery-speed enchantment into a permanent that is already online before either player has cast a spell, and the ability it brings is a pinger that taxes nothing but a single generic mana per cast. The payoff scales with how spell-dense the deck around it is: every burn spell, every cantrip, every cheap creature becomes a second damage source, and a turn that empties the hand can chip away a surprising fraction of a life total without committing anything to combat. The friction is real, though. Paying for each ping competes directly with the mana you would rather spend on the spells doing the triggering, so the card rewards a curve that leaves floating mana rather than one that taps out. As a build-around it sits in the awkward space between an enchantment that demands a deck full of cheap spells and a damage output that, ping by ping, rarely closes games fast on its own. The opening-hand clause is the whole argument for it: drawn off the top, it is a slow noncombat clock; in the opening seven, it is a free start to a death-by-a-thousand-cuts plan.