Congregate

Lifegain that scales off the entire board rather than your own creatures is what separates this from the fixed-chunk healing white usually gets. Timing is the operative detail: held until both players have committed bodies and an alpha strike is mid-swing, it harvests life from the opponent's army as readily as your own. On a stalled board with a dozen creatures dug in, the swing is enormous, which is precisely the position where a defensive deck wants to buy turns. It targets any player, so a crowded table turns every opponent's mana dork and token into fuel for whoever needs it. The cost of that scaling is the inverse of its ceiling: against an empty board it does almost nothing, making board state the real spell rather than the four mana. That even-handed counting (every creature, friend or foe, contributes) is the balancing weight, and it explains why white has returned to the board-counting lifegain template again and again without ever settling on a version that simply gains a reliable, fixed amount. The payoff is contextual, and the context is one the caster only partly controls.