2020-04-17 : For each applicable keyword, the appropriate counter may be put on any creature you control, including Kathril. The counters don’t need to all be put on the same creature.

2020-04-17 : Once Kathril’s ability begins resolving, no player may take other actions until it’s done and you’ve put +1/+1 counters on Kathril.

2020-04-17 : You check once for each keyword. If you have two creature cards with flying in your graveyard, you put just one flying counter on a creature you control, not two.

2020-06-23 : If cards in your graveyard have multiple hexproof abilities (such as hexproof, hexproof from white, and hexproof from black), a counter of each variant kind will be put onto a creature.