Manaforge Ultris is one of the five facilities that 'collect' the mana energies from the air of Netherstorm for Kael'thas' Blood elves. It seems that the blood elves did not build the buildings but only conquered them. This manaforge has been destroyed and taken over by creatures from the void. No apparent attempt has been made by Kael'thas' forces to retake the ruins.
Ultris is located on a floating island northwest of Tempest Keep.