Download it here:
https://www.dropbox.com/s/s7royvn7k4whanb/magicka.rar
- open the archive
- drag the batch file and the folder to into this directory (next to the magicka.exe):
...\Steam\SteamApps\common\magicka - start the batch file
So far you can play 14 modded maps, but I'll add more if there are enough requests:
1) Vulcanus Arena
2) Marshlands
3) Shrine
4) Havindr Arene
5) The Glade
6) Vietnam Survival
7) Cavern
8) Mirror Crystal Cavern
9) Volcano Hideout
10) Bout of Madness
11) Outsmouth
12) Element Roulette
13) World's End
14) The Invasion of Elwenhus
A guide for how to use the tool properly is accessible via the batchfile.
And while you're at it, do check out this
http://steamcommunity.com/app/42910/discussions/0/864946409178924036/
and this
http://steamcommunity.com/app/42910/discussions/0/540736781153355124/