We just played Dominion Nocturne and had the Idol victory card in play for the first time. As you see it has an effect that depends on the number of Idols you have in play.
From the Dominion Strategy Wiki on Gameplay under Buy phase I read that:
At the beginning of the buy phase, the player may play any number of Treasure cards from their hand, in any order, to their play area.
Does this mean that at the start of my buy phase, if I have multiple Idols on my hand, I can play them one at a time and first receive a Boon, then deal a Curse to the other players, then receive another Boon, deal a Curse, etc. for as many Idols I have on my hand?