Gelatinous Icosahedron

 Next up, another creature with firm roots in the fertile soil of real world mythology: the hippogriff. The Classical world certainly did love its animal hybrids. The hippogriff, a beast with the front parts and wings of an eagle and the hind parts of a horse, is a prime example. The entry in the Expert Rules is one of the shortest in all of B/X, and by extension, in all of D&D, at a mere four sentences. The first describes the creature's appearance, the second notes that it can be tamed and ridden, the third briefly expounds on its natural enemy relationship with the pegasus, and the fourth states that it nests in rocky crags. That's the full extent of it.  Stats-wise, the hippogriff is a moderately formidable opponent. Its AC of 5 and 3+1 Hit Dice are fairly stout, a little better than the average war horse. It is a swift flyer, at a movement rate of 360' (120') and somehow it manages to run almost as fast as a good horse on its eagle-talon forelegs. It's able...

 Time for another monster! We're still working through the H-critters, and next up is the hellhound. By the book, a hellhound is a large canine monster, reddish-brown in color and the size of a small pony ("That's quite strong, that is!" -- Eddie Izzard). It is impervious to normal fire, and highly intelligent (saving as a fighter of its full HD rather than half), often dwelling either deep in dungeons or in hot, fiery places such as volcanoes, and consorting with fire giants and other fire-loving creatures. Mechanically, the hellhound is a bit odd. Its Armor Class of 4 is quite a bit tougher than one would expect. Its Hit Dice run anywhere from 3 to 7; apparently whoever designed the monster either wanted it to be flexible with regard to the levels of parties it could be used against, or to create uncertainty for players, or perhaps both. Its physical attack is a pretty standard bite for 1-6 damage. Its movement seems a bit slow and lumbering at 120' (40'), e...