From publisher blurb:
Unicorn Island is a Fifth Edition plug-in adventure for four characters with an average party level (APL) of 3, 5, 8, or 11. This addon offers a general guideline on how to scale the adventure for each level. A famous big game hunter named Reginald Tolfree has opened a portal to the fabled Unicorn Island, where he intends to slaughter as many unicorns as possible. The characters must find Reginald and his band of hunters and put an end to his barbaric hunt.
Every child wants a unicorn, but where do they come from? What such honeyed land of rainbows and sweet thoughts exists in our dreary realm?
The truth is, unicorns aren’t native to this world: they are extra-dimensional creatures who venture beyond their sunny domain to bring peace and joy to us all. The portal to their realm is a closely guarded secret, for the unicorns know—perhaps best of all—the cruelty of men and their will to war. Many a unicorn have fallen to bands of mortal hunters, as their horns are extremely valuable. There are even rumors of special elder horns that are said to grant its wielder a single wish.
One such horn would be reward enough for any reasonable big game hunter, but Reginald Tolfree is no reasonable hunter. He has used his wish to rip open a permanent portal to the land of unicorns, and he hopes to hunt them all for his own selfish gain.
Somebody ought to stop that guy!