Neira the Necromancer is the Champion of the Unholy Terror Spawn. She will spawn, riding on an Undead Nightmare, once enough of her undead minions have been killed.
As Neira's health gets lower she will begin to run faster, trying to avoid her attackers. While she is running around she will also drop "unholy bones" on the ground, these bones will after a short while turn into a random undead creature.
The bones can be destroyed with a bladed item, like a dagger, before they turn into something more dangerous.
She will also throw the bones at her attackers to harm them directly.
When Neira is killed in Felucca, a Scroll of Power will be placed in the backpack of some of the players who damaged her. Additionally one of those who damaged her will also get a "Skull of Death", which is one of the six skulls needed to summon the Harrower.
Once Neira is killed the Undead Nightmare will disappear, so you cannot kill her and then tame it for yourself. You can also not use a bola to dismount Neira from the mount.
Neira's clothes and her red scimitar will also disappear when she dies.