Poppy

While Elder remains on the board, Flurry's one damage is lethal to enemy units at battlefields. It still damages your units too, so your one-Might Recruits die normally. Elder also makes damage from those small units lethal in combat. Its own play ability chooses up to one enemy per location, not every enemy there. Damage prevention can stop the hit completely, and removing Elder before the damage happens takes away the lethal effect. Keep the Dragon when the next cheap spell is supposed to clear the field.

Herald is Mighty, so Sacrifice can kill it as the spell's additional cost. Its Deathknell then plays a unit from your hand while ignoring Energy, but not Power. Elder still needs four Body Power and Harnessed still needs two Order Power. Herald's ability resolves before Sacrifice gives you its two cards and exhausted rune. Have the unit and its Power ready beforehand; the resources you are about to draw cannot pay for the earlier play.

Ruination kills every unit but leaves Gear in place, so Aurora and Armory can continue rebuilding afterward. Aurora reveals through the next unit, banishes it, then plays it without its base Energy or Power cost. Forge can recycle trashed threats before a later Aurora trigger, but it does not put them in a chosen order or guarantee Elder. Armory supplies bodies during your own open Main Phase, not as an opposing-turn surprise blocker. Make sure the reset leaves a route back onto the battlefield, not just a powerful base.