My headcannons for the giant clan as I believe that there's more to them than fighting
The only giant civilization we see in canon is Megadoza, but I like to believe that there are giant communities that live in the mountains and there's more giant cities around Scotland and Megadoza is the capital
The giants are Scottish, the giant communities all speak their own variations of Scots and Scottish Gaelic. Diane probably doesn't speak it as well because she spent a lot of her childhood living away from other giants, but she would have been re-taught it by Matrona.
Giants are mostly carnivorous, they like the thrill of hunting. Not a lot of giants are farmers or gatherers, but there will be a small minority of farmer / gatherer giants living on their own or in small communities.
The main entertainment for most giants are fighting related, e.g boxing, wrestling fighting festivals.
Being an orphan in giant society is pretty common as it is more likely that your parents will die in battle, so they don't really have a concept of family. They do tend to stick together as a community and come together around a campfire to tell stories about their battles and giant mythology.
A lot of their mythology revolves around Drole and their bravest warriors.
A lot of them have an interest in crystals and geology, they probably give cool rocks and crystals to their loved ones
They're surprisingly feminist and believe that women can be strong warriors
They have some giants who mine or blacksmith, that's probably the only other ways that giants earn money other than fighting for holy knights. I think they would value strength and hard work
They didn't have a monarch between Drole and Diane, they probably elect village chiefs every 250 years or so
giants have low birth rate because they are more likely to die in battle before they can get pregnant. They have a declining population because of this and due to the fact that they keep dying in battle.
When they commit a crime, the punishment is usually limb amputation/ execution for major crimes and whipping for smaller crimes.
Giants can get kicked out of the village if they're considered too weak. They probably will kill a baby if they think its too weak like the ancient Greeks did.
Similar to fairies, most giants are illiterate as they don't have an education and only learn to fight
The reason why giants value fighting is because during the holy war they had to fight to survive and they never stopped doing it so it just became part of their culture.
Giants put on war paint to battle. Each tribe has their own traditional style of war paint.
They believe in a concept similar to Valhalla, where they believe that dying in battle is the only noble death and any other death won't get you into heaven
Most of their clothes are made of the hides of the animals they kill
There are giant artists who are either commissioned to paint warriors and legendary battles on rocks and some who use their abilities to make sculptures by manipulating rocks and crystals. The second form is slightly looked down upon.
Giants mostly trade metals, weapons and animal meats / hides
Giants don't really have good healthcare as not a lot of them become doctors, so they have to go to a nearby town when they're ill. They might have battlefield medics who use herbal medicine, but outside of the battlefield they have little access to medicine. The battlefield medics will mostly deal with injuries and wounds, they're probably not as prepared to treat an illness.