Support

Support is a keyword action introduced in Oath of the Gatewatch that boosts your (or your teammates') creatures with +1/+1 counters. It was also used in Battlebond.

Description
"Support N" means "Put a +1/+1 counter on each of up to N target creatures." You may choose fewer targets at will.

If a creature (or any other permanent) has an ability that supports, the ability can't target the creature/permanent itself.

You cannot put multiple +1/+1 counters on one creature. If it has support 3, you have to put a +1/+1 counter on one creature, then another one, then another. It has to be a different creature for each +1/+1 counter.

Rulings

 * You can't put more than one +1/+1 counter on any one target using the support action.
 * Support can target a creature you don't control.
 * If a spell with support has other abilities that target creatures, those abilities and the support ability can target the same creature.