Glowing One

If a player is instructed to mill more than one card, Glowing One’s last ability will trigger once for each nonland card they mill during that instruction. For example, a player with four rad counters will mill four cards at the beginning of their precombat main phase. If all four of those cards are nonland cards, Glowing One’s ability triggers four times.

The cards are milled all at once, which means abilities that trigger “whenever one or more nonland cards are milled” will trigger exactly once as long as at least one nonland card was milled.

If a player has fewer cards remaining in their library than the number of rad counters they have when the triggered ability resolves, they’ll mill as many cards as they can.