For Warhammer: End Times - Vermintide, the DLC of Schluesselschloss gives you a single map for the last stand mode, the Schluesselschloss.
Your first task and challenge will be to pronounce it, then after that you will need to motivate 3 people to play it with you as the rewards for this, and indeed the entire last stand mode are at best mediocre and at worst nonexistent.
Luckily for them, they do not need to own it to play with you- As long as the host owns the DLC it is available to anyone who joins them.
The map itself is well made, with just enough supplies unlocking over time and many potentially great places to hold out, all of them flawed just enough to be a challenge. It looks pretty well, has a great view and is not too big or too small.
The price is a bit much for a single map, so I recommend only buying it if you want to support the game and developer. Otherwise, you will probably be able to find better value elsewhere