Dead World DLC - Death Worship + Undead is Ridiculous
Death Worship gives the infection spell to all of your heroes. Infection spreads all negative effects applied to an infected target to the entire army of the target. Negative effects propagate immediately and as best I can tell there is NO magic defense check on the any propagated effects...It lasts for the duration of the battle.
All Undead units have Terror, which causes the target to lose it's next turn.
Strategy to win every engagement ever (including epics when using starting units...): 2x mages, whole bunch of spearmen. First mage shadowbolts twice to reduce magic resist of the weakest magic def unit on the opposite team (to make sure infection/terror don't fail). Second mage casts infection, which requires a turn to prep. One of your undead spearmen then casts Terror on the infected unit. The ENTIRE opposing team is locked down for the rest of the fight and will be unable of doing anything at all. Just make sure to keep reapplying terror to the infected unit while you use spearmen to finish off the rest of the army because they can still counter attack.
I had to restart a match I'd dumped 4 hours into (and subsequently delete my custom race) when I realized it was pointless to even bother continuing--I was guaranteed to win literally every single tactical encounter using nothing but my starting units and it had become a tedious jaunt to the finish line.