Hades skins feature small graphics of ancient Greek helmets painted all over the weapon's body. The weapon itself is a solid grey color, while the helmets are cream and appear in several designs. The Hades skins family consists of only one skin - Tec-9 | Hades. It was added by Valve in the Operation Bloodhound update in May 2015 and belongs to The Gods and Monsters Collection. As such, it can no longer be found in any case but can be purchased online. The skin can appear with any exterior ranging from Battle-Scarred to Factory New.
As far as the skin's value goes, it depends solely on the exterior, ranging from around $6 to 12 dollars.
Check out other CS2 skins families: