Frontline Medic
Creature — Human Cleric
Battalion — Whenever this creature and at least two other creatures attack, creatures you control gain indestructible until end of turn.
Sacrifice this creature: Counter target spell with 
in its mana cost unless its controller pays 
.
Willian Murai
Commander 2020 (C20)
• #89Rulings
The three attacking creatures don't have to be attacking the same player, planeswalker, or battle.
(wotc • 2024-01-12)
Creatures that come under your control after Frontline Medic's battalion ability resolves will not be granted indestructible by this effect.
(wotc • 2013-07-01)
Once a battalion ability has triggered, it doesn't matter how many creatures are still attacking when that ability resolves.
(wotc • 2013-04-15)
The effects of battalion abilities vary from card to card. Read each card carefully.
(wotc • 2013-04-15)
Rulings
The three attacking creatures don't have to be attacking the same player, planeswalker, or battle.
(wotc • 2024-01-12)
Creatures that come under your control after Frontline Medic's battalion ability resolves will not be granted indestructible by this effect.
(wotc • 2013-07-01)
Once a battalion ability has triggered, it doesn't matter how many creatures are still attacking when that ability resolves.
(wotc • 2013-04-15)
The effects of battalion abilities vary from card to card. Read each card carefully.
(wotc • 2013-04-15)