So basically the first part of the story is a summary of your life as a ceadeus that protected an island from invasion and from the larger sea monster causing that to be you myth(atlantis) when you are summoned you have a human body similar to that of Asterios but a bit more down scaled but you still have the beard and awesome looking horns.

your abilities is summoning weapons made from your self and manipulating water

your noble phantasm is summoning the underwater temple slash arena where it was dubbed as your resting place and then transforming into your monster form and blasting them with a beam of water.

you wear you armour in your human form begging from low rank and then to g rank as you get ascended by Gudako.

low rank (without helmet on)

G-rank (without helmet on)

only characters from greek mythology will know who he is when he uses his noble phantasm.

his reputation in Chaldea

the caring grandfather even if you have a young adult face making you resemble 25 years old.

care taker of the servants that resemble kids i.e jack, lily jeanne, lily artoria etc..

Lushes majestic beard that Gudaku will sleep in.

(secret until master finds out) master chef in cooking food from the world of monster hunter (which fans know is a large amount) is like by all the Saber faces even if the Artoria's ... like him too much.

will be forced to become santa reason already known.

so thats it I will work on stats if people like this idea.