Here’s a monster for ye olde D&D.
It looks like a man who was first gene-spliced with a hairless gorilla and then fed steroids his whole life, in doses high enough to kill elephants. It’s basically a still living muscle-golem. The head is painfully shrunken, lacking almost any features except for round, -shark-like eyes, and a wide mouth filled with teeth like gravestones.
Often used for harsh manual labor, due to their immense strength (STR 22, to be exact). They lift rocks, shovel earth, and so on quite quickly, though their endurance isn’t great.
Sometimes they are used as guards. They can quite easily kill a man with their fists (which hit like sledgehammers), or with actual weapons (which, if more powerful, have a tendency to break due to overstrength). Their fragility is a problem.
A few vain people use them as nutcrackers. No, not their mouths (though their jaws are strong), because that’s unhygienic. They crack nuts between their pectoral muscles.
One must be careful. When a Musclebeast is pushed too hard, it can bring all its strength into the fray by mistake (it’s not that smart), and tear its skin and joints apart with the massive power of its contracting muscles.
HD: 2 (15 HP)
AC: 10 , or 1  if in its super-heavy plate armor.
Intelligence: as a clever dog
Attacks: fist (1d6+2), sledgehammer (2d6+3, breaks on any 5 or 6 rolled).
Hyper-strength: STR 22. If it rolls a natural 20 on an attack roll, it deals triple damage and also takes 1d6 damage itself. Natural 20’s on strength checks damage them as well (and move mountains).
You feed a baby magical steriods… basically. The muscle growth’s the easy part, and then the problems come in when you’re trying to reduce heart failures and increase joint strength. Often they are kept in strethching tanks and injected healing potion continually to build up tendons. It takes about five years to grow one (or a month, if you’re doing it the quick and dirty way, though that reduces its life span to 1d6 years and doubles the overstrength damage).
Not much really. Food and a place to sleep. Easily attatched to their master/creator. It’s quite hard to get it to wear clothes (though there aren’t any “vitals” to hide). They like exerting themselves on monumental tasks. Would happily push an infinitely heavy rock up a mountain forever. If angered, charges like a derailed train and crushes things.