The Suntower is a tower near Ab'Dendriel, you can find it here where you can find the NPC Edala who sells the Blessing The Fire of the Suns.
Note that he does not sell Blessings on pvp-enforced worlds like: Inferna, Dolera!
Suntower NPCs
Suntower Pictures
See also: Suntower (Guildhall)