Accidental(?) devil summoning

yourplayersaidwhat:

Context: I was DMing a mini campaign where everyone had to make gritty/edgy/dark characters (and surprisingly enough everyone brought something different to the table). They are long resting at a desert oasis.

DM: “ok what is everyone doing now?”
Dragonborn: “I sit in a corner and light candles around myself as I pray to Tiamat”
Elf(?): “I do the same but far away from him”
Dragonborn: “if we had more people we could make a pentagram”

Queue silence as everyone starts thinking the same thing, announcing who has candles and torches

Set up is complete, they succeed a religion roll and I flip through the devil section of the Monster manual and roll for which one they get.

DM: “A woman clad in black armor and surrounded by her own dark wings emerges from the Oasis pool-”
Everyone cheering: “WE GOT THE HOT ONE!!!”