Whenever a player casts a spell, you may put a +1/+1 counter on this creature. At the beginning of your upkeep, you may move any number of +1/+1 counters from this creature onto other creatures.
原文Forgotten Ancient's last ability doesn't target any creatures. You choose how many +1/+1 counters will be moved (and onto which creatures) as the ability resolves. Notably, once the ability starts resolving and you make these choices, no player may take actions until the ability has finished resolving.