Laelia, the Blade Reforged

The last ability triggers only once for each time cards are put into exile from your library and/or graveyard, no matter how many cards were exiled at the same time.

If a player is instructed to exile cards from their library "until" a certain event occurs (for example, because of the triggered ability of a spell with cascade or discover), that player exiles those cards one at a time. Laelia's last ability will trigger that many times.

You must follow the normal timing permissions and restrictions while playing the exiled card. If it's a land, you can't play it unless you have land plays available.