Swarm the city - dlc

Heart of Thundering Python is an ultimate artifact that once belonged to the Kingdom of Mist. A silver hammer is encased in this transparent heart, emitting bursts of lightning constantly. Two streaks of python-shaped lightning surround the silver hammer, feasting on the bursts of lightning incessantly. This lost artifact is the key to unlocking mighty lightning powers for your zombie generals.
The Heart of Thundering Python DLC contains the following content:
Flamewalker will turn into Lightning Flamewalker and a blue lightning aura will enshroud its body. Zombies converted with Flame Impact and the fireballs summoned from Rain of Fire will have additional blue lightning effects and deal a small amount of extra lightning damage.
Amalgadon will turn into Lightning Amalgadon and a golden lightning aura will appear around its fists. Brutal Weapon attacks and Amalgadon Sphere will have additional golden lightning effects and deal a small amount of extra lightning damage.
Corrosion Lich will turn into Lightning Corrosion Lich and a red lightning aura will appear around the gems on its staff. Bone Spike and Expanding Vines will have additional red lightning effects and deal a small amount of extra lightning damage.
Frost Warrior will turn into Lightning Frost Warrior and a purple lightning aura will appear around its razor-sharp axes. Weapons summoned by Weapon Drill and the ice spikes created by Icicle Blizzard will have additional purple lightning effects and deal a small amount of extra lightning damage.