"A pale blue staff that always seems cold to the touch."
It has a fantastic +151 weapon attack for any Mage that wears it, even higher than the Auktufiti's Ballista. It can be equipped at Level 45.
"Empower Magic Missile to launch Mana Stars."
The Perk of the Astrologist's Scepter is Twilight.
It turns Magic Missile into Mana Stars, making them deal much more damage and appear like shooting stars when you launch Magic Missile. The number of Mana Stars launched greatens with the perk, with it increasing from 1 -> 2 -> 3 to 2 -> 4 -> 7.
As in the description, the whole staff is a light-blue periwinkle. It has a white orb on top with four feathers hovering around it.