An Old God's Soul

Son of Morrigan and one of my DA PCs, the happy-go-lucky anarchist Damion Amell.

-spoilers-

If you did the ritual with Morrigan before the final battle with the Archdemon she actually has your child (or Alistair's if you're female and convinced him by some miracle to go through with it)--she explains it essentially as instead of the Archdemon's tainted Old God soul being destroyed along with the Grey Warden it is drawn to the unborn child but sans taint.
Pure Old God before the Taint darkens it.
If you have the Witch Hunt DLC you find out that the child is a boy.
This is a rough draft for maybe a Dragon Age comic I may or may not end up doing. <: