Embercleave

Flash
This spell costs {1} less to cast for each attacking creature you control.
When Embercleave enters, attach it to target creature you control.
Equipped creature gets +1/+1 and has double strike and trample.
Equip {3}

The List

Throne of Eldraine

Throne of Eldraine Promos

If an attacking creature with double strike and trample destroys all of its blocking creatures with first-strike combat damage, all of its normal combat damage is assigned to the player or planeswalker that creature's attacking.

If there are no creatures to attach Embercleave to when it enters the battlefield, it simply remains unattached.

If you cast Embercleave outside of your combat phase, its cost won't be reduced.

Once you announce that you're casting a spell, no player may take actions until the spell has been paid for. Notably, opponents can't try to change by how much a relic's cost is reduced.

The cost reduction ability reduces only the generic mana in the relic's cost. The colored mana must still be paid.

To determine the total cost of a spell, start with the mana cost or alternative cost you're paying, add any cost increases, then apply any cost reductions. The mana value of the spell remains unchanged, no matter what the total cost to cast it was.