I feel like this would be a cool idea for a barracks which could dominate the battlefield under the correct micro management and support.
Name: Dark knight hall
Upgrade cost: 250
Health: 220
Damage: 9 - 11
Armour: High 75%
Respawn Time: 18 seconds
Bloodbath:
I feed on your pain
170 gold per level
Heals 20/30/40 health per unit killed within a medium range
Dark Arts:
What does not kill me...
250 gold
Gains 15 health (heals by 7 and his max health goes up by 7) and +2/+3 attack every time a unit he is fighting dies. The stats are for a single knight. When the unit dies the respawned knight will not have the buffs
Self-Preservation:
Pick your fights
150 gold per level
Has a 11/23/35 % chance of swapping an engaged enemy unit with a weaker unit further from the exit when health is lowered to under 40%.