Zaltais was a servant of Nalar who was simply the outcome of the dreams of the Dark God as he resided in his exile outside the known universe. Zaltais was sent by Nalar from the seventh chamber of the Void to Midkemia in order to control and manipulate Fadawah, who unconsciously served the Dark God.
After the defeat of Jakan by Pug and his comrades, the SerpentWar still continued and Fadawah and his army invaded Yabon. Jorna, who had long ago left the body of the Emerald Queen and taken the form of Kahil, the advisor to Fadawah, performed a great spell to raise the dead in order to fight for Fadawah and this spell was heard as a prayer by Nalar and the Dark God sent Zaltais from the seventh chamber to Midkemia to make sure that everything advances as planned. When Pug, Tomas, Nakor and Miranda entered Fadawah's headquarters in Yabon, they were challenged by Zaltais who called himself an angel sent by the Gods - no doubt that it was not the Gods but only Nalar who sent him.
Zaltais was a very powerful creature, which was impossible to be killed due to the fact that he was coming from another reality. The four comrades did their best to defeat him and he was sent back to the rift which opened to Nalar's realm. As he was a product of Nalar's imagination, Zaltais was something alien to even Tomas, who admitted that neither him nor other Valheru had ever encountered such as creature before. In addition, he was the most powerful means Nalar ever used in his never lasting attempt to destroy Midkemia.