CR 17+ aberration creatures from Monster Labs. These public stat blocks fit that band of the table; remix the CR or abilities if your party is ahead of the curve.
Zargon, the Returner
CR 30 · Aberration
Prukal, the Dark Globe
CR 30 · Aberration
Pandorym, the Consumer
CR 30 · Aberration
Mak Thuum Ngatha, the Nine-Tongued Worm
CR 30 · Aberration
Father Llymic, the Alien Thought Given Flesh
CR 30 · Aberration
The Eldest
CR 30 · Aberration
Atropus, the World Born Dead
CR 30 · Aberration
Ihbar, the Eternal Galaxy
CR 30 · Aberration
Acamar, the Star Consumer
CR 30 · Aberration
Y'chak, the Violet Flame
CR 30 · Aberration
Shothotugg, Eater of Worlds
CR 30 · Aberration
Piscaethces, the Blood Queen
CR 30 · Aberration
Holashner, the Hunger Below
CR 30 · Aberration
Bolothamogg, Him Who Watches from Beyond the Stars
CR 30 · Aberration
Gorathil, the Amber Hulk
CR 30 · Aberration
Kezef the Chaos Hound
CR 30 · Aberration
Dendar the Night Serpent
CR 30 · Aberration
Shub-Niggurath
CR 30 · Aberration
Nyarlathotep
CR 30 · Aberration
Yog-Sothoth
CR 30 · Aberration