Magicka: Dungeons and Daemons is a DLC that brings players to a completely new location without leaving the comfort of their home. Literally, as players will be venturing into the dungeons of Castle Aldrheim to defeat what is possibly the hardest boss there is.
Official Info from Steam Page
Something stirs beneath Castle Aldrheim…
Deep in the sub-dungeons, long forgotten by the Wizards, the demented ancestors of the Aldrheim Order have awoken an ancient evil. The fate of the world has yet again fallen on the shoulders of our haphazard and colorful wizards. Will the Wizards survive as they stumble upon Aldrheim’s most secret of secrets?
Explore never before seen places in the fantastical world of Magicka. Test your mettle against new enemies and try to avoid getting slime all over your robes. Where does that even come from? It’s everywhere! If we could reveal the super-secret hard mode, it would attract even the most battle-hardened wizards. Unfortunately, it’s a secret, so we can’t talk about it.
Things to know
This challenge can be played by 1-4 players and introduces several new achievements. It consists of a large dungeon with various monsters with the final boss being the Wurstmacher. There are two new monsters in this challenge - one is a fiery goblin wielding a blaze sword while the other is a Slime (name unconfirmed). There are four main levels in this challenge: The Sub-Dungeons, the Library, the Courtyard and the boss room.
Note that you are not playing your original characters from the campaign and the DLC The Stars are Left, as evidenced that you don't have a beard. Well, they are still stuck in R'lyeh...
Walkthrough
The game starts with Vlad telling of how he "heroically" "saved" Midgard from certain doom by defeating Cthulhu (jerk). The wizards have decided to throw a great party in his honour, but just like the party 20 years ago they have once again run out of cheese. They've sent someone down to the dungeons to get some but they haven't returned, so the Headmaster decides to send the people with the fancy robes down to see what's the matter.
Cellar: Sub-Dungeons
The game then throws you into the cellar of the castle and you start off with only one magick, Revive, this time. You will first encounter some fire goblins, who will set you on fire with their sword and are also very resistant to damage (even the trusty 
barely does any damage). Of course, logically they take more damage from cold, so it is suggested you incorporate that into your spells.
The next room is where you will find macaroons/cheese, but also Mort'en lying on the floor with lots of blood by his side. Turns out, an evil daemon known as the Wurstmacher has dragged off everyone else and left him for dead. Vlad then magically appears (if he can do that why can't he come down?) and tells you that you will need to defeat this Wurstmacher and avenge the fallen. Mort'en he will "take care" of. If you kill Mort'en though, he will respond with a disappointed "Oh. What a waste." and disappear.
The next area is filled with more fiery goblins, as well as regular goblins, wizard goblins and also a few orcs. This area might prove challenging, but an important thing to note is to always be safe 
+ Self and kill the goblin wizards first, as their Nullify and water bolts make them have an extremely high annoyance value. It might be worth picking up the goblins' Frost Cleaver as it could be handy later on. The rest of the level is much of the same; use any spells that you like to dispatch of the goblins, orcs and other enemies until you come to a room with a lever/pulley/turnstile. Once you activate it, rats will come out. Eek! Actually, there's no need for panic, as they have extremely low HP and even a basic spell such as AoE will take care of them quickly. Once you've done away with the rats, backtrack a bit and you'll see that a previously unlocked gate has opened, allowing you into the next level.
Old Library: A Forgotten Storage For Books
The old library features mainly goblins and wizard goblins, as well as some orcs. Again, use the same methods you used in the last area to dispatch of the, but be warned that the numerous bookshelves along with the larger amount of goblin wizards can make this an even bigger challenge. Try not to get yourself trapped in a corner. Seriously, don't. The best way to dispatch of them is to use either the Super Steam Beam (Force/Area/Weapon cast ) or the Arcane Lightning Shields (Weapon cast 
). You will reach a big pit, and it might be worthwhile turning left and grabbing the Haste spellbook before heading down.
The next portion of the map features orcs, but note that due to the very enclosed space as well as more obstacles you can easily become trapped (again, take note: DO NOT GET YOURSELF TRAPPED.). However, you can use the narrow openings to your advantage, casting some high damage AoE spells or walls of fire/frost/flame/arcane/lightning. At least they'll all huddle around. There is a checkpoint here, so be sure to grab that. You'll need it. Head on around and you'll see some more orcs, as well as a troll. At least it's a bigger space now, so feel free to use some more powerful spells. After defeating the troll, the very top corner will have a Sacrificial Dagger, which is the same one is the swords the Cultists wield in Magicka: The Stars Are Left. Then you will find that you have eventually looped back to (almost) where you started, because of a suspiciously convenient blockage. There will be some final goblins here, but they should prove no problem as they're standing right next to a pit, so just use Push (Right click) and knock them into the abyss. Behind you is a staircase blocked by some fallen wood, so use either or 
to blow it up and continue.
The next area features another new enemy, the slime (name still unconfirmed). They will duplicate into four smaller versions of themselves once they are 'killed', so again watch out as their increasingly large numbers can overwhelm you. Oh, and there's a goblin wizard too, because. Anyway, after you killed the slimes, you might want to head up through a narrow crack into a semi-secret area, where you'll see a dead...something with a sword, The Riddle of Steel. If you walk too close to it, though, some undead will appear behind you. remember they take damage from Life and heal from Arcane, so some healing mines 
or healing walls should kill them all. Well, not really, since they're dead in the first place. However, onto the next area, the Courtyard.
Courtyard
This is the last level of Dungeons and Daemons before you reach the boss. Once you enter, head left to pick up a sword (I forget which). Then, you move onwards to another closed door/barrier (again) and also some fire. Behind the fire is the pulley to open the door, so either put out the flames with 
or cast on yourself before barging in. Once the door is opened, you will come into an intersection with four doors and a well with a skeleton sitting on it. Now, be careful not to - you knocked the skeleton down, didn't you? Oh well, at least it got the door opened - or rather, smashed by a troll. Its worth noting that to the left of the well after opening the door there is a weapon just inside the door.