Lotan

Pre-Splatoon 1:

Lotan was created and raised to be a sentient super-weapon. His special limiter was de-activated by tartar through partial sanitization, and he is stronger than most octolings in terms of ink resistance and ink power. He, however, cannot produce much ink without using a super, and can only refill via super or picking up a refill. 

splatoon 1:

he's a child lol, not old enough to be fighting. He learns a lot about both octarian and inkling societies and technology because of the internet and magazines left behind by subway passengers 

splatoon 2:

~15, has started running through more dangerous tests at this point

Octo expansion:

Finds a way out of the subway after it was destroyed, spends a considerable amount of time trying to adjust on the surface

post octo expansion:

works for sheldon developing weapons, and creates dualies for himself that produce their own ink. Takes up a side job for grizz for extra cash and ends up getting close to grizz because of the amount of golden eggs he brings in. Eventually ends up starting a band with Clarion under a stage name because he's inspired by Marina. He performs using a mask so that no one will recognize him off stage.

Splatoon 3 (non-canon, personal storyline):

His band starts taking off, meanwhile a full fledged war is brewing between octarians and inklings. As someone who knows much about the octarian's military strategies and technology, Lotan ends up enlisting and fighting the octarians as a soldier. The squid sisters recruit him as an agent where he finds a way to weaponize music, taking inspiration from Pearl's killer wail. He and his bandmate start using that technology to gain terf, and gain a considerable advantage in the war.