I've been running the AD&D 1e version of The Temple of Elemental Evil in 5e.
My players have taken the secret tunnel from the tower and found the passage to Dungeon Level 3—I believe completely by in game action because I don't think they have the source material—and are about to turn the corner into the illusory Basilisk.
The heroes are about to encounter an illusory creature that will be capable of petrification on a failed save. I'm having trouble matching the 5e spell that would replicate the 1e effects. The nearest spell I've found is Phantasmal Force.
Yet Phantasmal Force is only described as having a limited duration and no increased duration when cast at higher levels. The description in ToEE clearly makes it out as permanent illusion, or at least one that is not held in concentration by a magic user on watch.
Am I missing a better spell? I stopped the session as they reached the landing of the tunnel just as they are about to enter. I want to get these next actions to work in system for fairness.
NB. I am the DM