Nercromancer Tech is a Tech introduced in the 9.9 Alpha test update and removed a few months later during a match on cp_yukon_final when it was voted to be Turned off forever.
It returned in the v10.0 update as a reworked version
Skeleton Health: This wouldve boosted the Skeletons health but it ever fully functioned correctly
Skeleton Damage: This boosted the Skeletons power (Damage) to Players and Buildings.
Spawn Count: Increased number of skeletons at a time
Skeletons could enter the enemy teams spawn and not count as a spawnkill, thus no ION Cannon would be deployed.
Standing bellow the control point on nucleaus could make the skeletons become a permanet defense as they got stuck and were unkillable and unreachable.
Engineers could become a necrospawner and stay inside spawn while deploying endless ammounts of zombies
2016: Added Nerco Tech
(Unknown Time): Added a recharge for Nerco Spawn
(Unknown Time): Nerfed damage
(Unknown Time): Removed Nerco Tech by disabling them forever
Trivia: Their "Eheheuheueh" sound could be heard from any part of the map, annoying lots of players