Hengars! The _GOD_ monsters in MR1! Well, in my not-so-humble opinion, anyhow. However, out of all the monsters, they are probably the most complicated to get. Maybe not the hardest as such, but easily the most complicated.
Ever been searching in the desert expedition, and found those wierd arms and legs? Well, those are the key to making the Hengar. When you have managed to get all the arms and legs (one left arm, one right arm, one left leg, and one right leg), you'll get a chance at an invitational. There is where you can get the head. Of course, as with the typical invitational, getting the win is a hard thing, since you're fighting a Hengar. Take a good intelligence/speed critter in is my best suggestion.
Now, once you _have_ the doll, there's another problem. You can't just use it as a seasoning and make a critter. First, you have to get a creature with high intelligence into the desert expedition once more (or previous to getting the head, if you're lucky). There is a tablet around the center of the desert with writing on it. A high intelligence monster can read it, and if it can read the tablet, then it has now become the 'marked' monster. That is the only monster that will make you tyour Hengar. Well, that or any other monster that can read the tablet, of course. Take that monster, blend it with another and that statue, and you have yourself a Hengar.
Hengar are what I call the 'god' monster because of their high skill, good defence... just all around good stats in general. Plus, they have _incredibly_ long lifespans, and are well worth every moment. Besides, their little floating UFO form is just too cute to be believed.