From publisher blurb:
Avast! Here be a suppl'ment for Yarr! Pirate RPG!
Everyone knows Pirates and Ninjas have always been mortal enemies (like, duh). Now, for the first time, you can enjoy the added realism and opportunities for historically accurate role-play by adding ninjas to your pirate adventures on the high seas.
While Avast! Thar be Ninjas! has a fun, goofy tone (an April Fools day confection), it can be taken seriously with three new classes, new spells, and new rules for poisons.
Compatible with Yarr, Dagger RPG, and all or most OGL / OSR / d20 games, and formatted to print a nice digest-sized booklet.