Phantasy Star Universe
"Beasts have stronger physical abilities, and can transform themselves through 'Nano Blast.'"
Phantasy Star Portable 2
"A race genetically engineered to survive in the harsh climates and working conditions of the mines on Moatoob.
They are said to have strong senses of family and loyalty and can be distrustful of other races.
On average, their physical abilities are significantly greater than other races, and they born with the ability to nanoblast, a technique by which they transform into a larger, more physically powerful form."
HistoryBeasts were purposely created by combining human and monster DNA in order utilize them to work hard labor. With their bodies being strong and capable of withstanding the harsh Moatoob environment, they proved much more efficient working the mines that other races.
Some Beasts are Small, meaning that their bodies don't grow to a full adult size.