Kelsien, the Plague
Legendary Creature — Human Assassin
Vigilance, haste
Kelsien gets +1/+1 for each experience counter you have.
: Kelsien deals 1 damage to target creature you don't control. When that creature dies this turn, you get an experience counter.
"Aim for an eye. Better they never see you."
Chris Rallis
Commander 2020 (C20)
• #11Rulings
If the target of Kelsien's last ability dies before the ability resolves, you won't get an experience counter.
(wotc • 2020-04-17)
Each time Kelsien's last ability resolves, it creates a separate delayed triggered ability. If you untap Kelsien and activate its last ability multiple times in one turn, they'll each trigger when the appropriate creature or creatures die.
(wotc • 2020-04-17)
If Kelsien leaves the battlefield, you keep any experience counters you've received.
(wotc • 2020-04-17)
Rulings
If the target of Kelsien's last ability dies before the ability resolves, you won't get an experience counter.
(wotc • 2020-04-17)
Each time Kelsien's last ability resolves, it creates a separate delayed triggered ability. If you untap Kelsien and activate its last ability multiple times in one turn, they'll each trigger when the appropriate creature or creatures die.
(wotc • 2020-04-17)
If Kelsien leaves the battlefield, you keep any experience counters you've received.
(wotc • 2020-04-17)