Gigantic, cosmic, tentacled entities first described in the D&D Immortals Set, where they are among the most powerful creatures in that multiverse.
In a forum posting, Frank Mentzer mentioned they resembled certain beings from Lovecraft's Cthulhu Mythos, without naming which:
I'm sure draeden arise somewhat from Lovecraft, exhibiting two similar traits to a certain race therein: the unspeakable horror if seen in true form, and their arrogant superpower attitude that small mortal things aren't even worth noticing (except to occasionally and utterly destroy after driving them mad).
They resemble Cthulhu's star vampires and Nyarlathotep.
The name may come from the Middle English Dræden - 'to dread, to be afraid'.