There are encounters like the second of Prison of Khinn or the first of Shadowfall Mountain in which monster groups are not placed at the beginning but appear as reinforcements during the encounter. Is it possible to play Enchanter cards on monster groups that are not yet on the map?
If it is possible, would it be possible, after having played Sign of the Last Zenith on group 2 that is not yet there, to "cycle" Rings of Zhol'Alam by playing it on monster group 1 also not yet placed, move it immediately to group 2 since there is no monster from group 1 on the map, draw a card from Sign of the Last Zenith, then discard the Rings for good since there is no monster from group 2 on the map either?
Also, is it possible to play Enchanter cards on monster groups that are no longer on the map and that can't be reinforced? I'm asking because in cases where only monsters from 1 group remain on the map, playing Sign of the Last Zenith on a monster group that has been entirely decimated (after all, it can be the last card in the deck...) would at least allow some card drawing.
I prefer to ask in case the heroes ask me what the heck I'm doing, because some of these plays seem quite tricky to me.