Mini-Dungeon adventure for 4-6 characters of levels 9-11
A rebellious voidling in service to the void dragon Malinda set up the perfect ambush and devised a mechanism that transported the dragon into an extra-dimensional time-stasis chamber just before the killing blow was delivered. Once time was restored in the chamber, the dragon would be dead, and the voidling would be spared instant death when the dragon detonated.
The transport happened as planned, but somehow the dragon and chamber manifested on the Material Plane inside the temple cave complex of a sphinx. The sphinx sealed the chamber, refusing to open it until one of its three riddles was answered out loud; it refuses to accept answers telepathically.
The voidling needs help so it summoned the Void to these caves, knowing that the havoc caused would bring in the nearby villagers to investigate. They would be easy to dominate, and their deaths would be of little consequence.
It did not expect adventurers.
Mini-Dungeons are short, setting-agnostic adventures for 5th Edition which can be easily inserted anywhere in your campaign.