16 Apr 2021
Breena's triggered ability will trigger even if you control no creatures.
16 Apr 2021
If the attacking player is one of your opponents and has less life than the player being attacked, then the condition is satisfied.
16 Apr 2021
You choose which creature to put +1/+1 counters on as the ability is resolving. Once you make the choice, no player may take actions until the counters are placed.