Störtbeker is printed in the Munchkin Booty color scheme but may be used with any of the Munchkin card games.
The card is named after Klaus Störtebeker, a 14th-century privateer and pirate.
A rough English translation of the card text is:
Will not fight Pirates who are under level 5.
Bad stuff: Yes, he's a pirate, but fair. That is why he only takes the rounded half of your items, you choose, which ones. Discard them.