Revenant

"The boomerang man"
== Cost & gain ==
One revenant base cost are : 
* 9e401 Gems
* 6e9 Black Widow (the lower rank undead)
* 1e50 souls
* 1e6 raw mana
It's also give you : 
# The next undead (the Draughr)
# 2 Black Widow/sec