This is hades, he is the god of the underworld which means he has to keep peoples souls in there.
When Rhea told Cronus she was pregnant Cronus was furious. So Cronus ate up his children including Hades. Rhea was mad, so she kept the birth of Zeus a secret.
Rhe prepared a special poison that would make Cronus throw up the children.
Once hades and his brothers took down Cronus, they each had to rule one part. Zeus was lucky and got the sky, Posiden won the water, and Hades, unfortunately, got the underworld. The brothers sometimes had wars but their only enemy was their father Cronos.
One day Hades met Persephone and fell in love. So Hades took her down to the underworld to be his wife. Then they eventually had kids