You know that Scryer can be found in Winterspring.
Quest Text Edit
"We are Deathwing's children, whelp. Our dominance over the lesser Aspects must be enforced.
If you are truly worthy of ascension, the lesser dragonflight will wilt in your presence.
Find their champions and lay waste to them in the name of our Father!
Travel to Winterspring and track down the mighty blue drake, Scryer. Crush him and any of the Blue Flight that stand in your path. Tear out his skull and return it to me."
Scryer is in the back of a cave filled with blue dragonkin in Mazthoril, south-southwest of Everlook. There is a rune on the ground that will teleport you to the top of the mountain, so take care not to wander on to it during the fight.
This quest was a part of the Onyxia's Lair attunement chain.
- Patch 1.3.0 (07-Mar-2005): The Test of Skulls for Scryer, Somnus, and Chronalis can now all be obtained simultaneously.