Magicka: Grimnir's Laboratory

Official info from Steam page

Deep under Castle Aldrheim lies Grimnir’s laboratory, a secret long kept from all Wizards of the order. A crazy-random happenstance during recent “cellar activity” has caused the wizards to discover this long lost lab and all its horrors!

Fight against 16 waves of monstrous foes on an all new map. Experience a new twist on the traditional challenge mode with elemental alters that dictate what spells and elements can be used. Three new doctors, in oddly familiar robes, have come to your aid in defeating the hordes. Will you and your friends be able to survive Grimnir’s horrors?

Contents

 * A new challenge against 16 waves of monstrous enemies
 * Elemental altars control spell usage
 * New enemies: Grimnir’s long forgotten experiments
 * 3 new robes give you a unique experience of playing a certified Doctor:
 * Dr. Quake: Clad in armor and armed with two lightning dispensing gloves. Just make sure to stay away from lightning yourself
 * Dr. Terrible: A lab coat with good protection from the elements, a Death ray and a Trans-matter staff. Everything one needs for **a doctorate
 * Which Dr.: Sporting a brown blazer, a trendy scarf and a nice red Fez, the latest in fashion. With a Sonic Tuning Fork and a **Magickal piece of paper, this wizard is fully prepared for any time travel