Flashbang (5e Trap)
From D&D Wiki
This trap consists of a rune stone that when activated (either by stepping on a pressure plate, button...etc. Can be any trigger. DM decides), a strong flash of light infused with magical energy is bursted at everyone in the room. If you have direct eye contact with the rune when activated, make a DC 17 constitution saving throw. Else, if a wall covers you (half or three-quarter cover) you only have to make a DC 14 saving throw (constitution). Or else with full cover (but however still in the same room), make a DC 10 saving throw. If there's a feature or feat that your character or other creature posseses that enchances its eyes and vision (For example in the barbarian Archetype class, path of the totem warrior: Eagle’s Eyes: You do not suffer disadvantage on Wisdom (Perception) checks made in dim light. Additionally, you can see objects up to 1 mile away as if they were up to 100 feet away from you. This feature enchances the barbarian's eyes therefore, he/she'd be affected), you/the creature have disadvantage on this saving throw. If failed, the creature is blinded for 1d4+2 hours and cannot sleep while blinded. The magical energy infused into the light affects your character's mind and it cannot sleep unless knocked out cold. If saved, the creature only suffers a few seconds of blindness unless the saving throw of the creature has a score higher than 20 (or in a natural twenty). If the creature rolls a critical failure, the duration of the effects double.
If a creature does not have eyes or is already naturally blind it automatically saves.
If a creature has more than two eyes it has disadvantage on the saving throw.
Suggested Edit: "This trap consists of a rune stone that when activated emits a strong flash of light infused with magical energy at everyone in the room."
This trap is nice combined with an ambush with creatures (that don't have eyes or are blind so that they are not affected) to attack the players while surprised in the first round.