Behemoth: Land of Titans

Every village has a giant that protects it. If that giant dies a new one will be born into that village. They're a weird cross between a Shinto-style deity and a protector spirit with a bit of Elemental, empowering a human being. They require significantly less food than their size would indicate.

Giants are always born of normal parents. They achieve a growth spurt when "chosen", which is slightly different depending on cultures. The power of the growth spurt can also vary depending on the needs of the village, but at the very least a giant isn't likely going to fit in any houses. During their growth spurt they have trouble with appetite, but as time goes on this wanes to being virtually nonexistent.

Primary foe of Giants is Dragons, but other gigantic creatures exist. The primary goal of a Giant is to protect their settlement. Giants without a settlement (either due to downsizing of the settlements rendering them superfluous or due to their settlement dying off), can go about doing other stuff, but will eventually die.

A village equips their giant(s) as an indirect form of social competition or warfare between settlements. Periodically, giants in a related area would meet up in order to know each other in case of larger threats.

Giants are traditionally just large humanoids, but regional variations in size and shape exist based on the needs (and potentially worship) of their people. This can change over multiple generations of giants in the same location.

The qualifications for a giant to appear in a settlement are:
>At least 100 people
>Village must be able to sustain the giant
>Village must be able to equip/clothe the giant