In developing these groups, I've noticed that so far I have two traditionally protagonist races (dwarves, elves) and two traditionally antagonist races (giants, trolls) as well as the two races I haven't yet assigned recognizable parallels. Still not sure what I'm going to do about that.
Giants in this setting live in villages mainly along ocean shores, although -- see that river there, in the middle of the image? -- that's probably a good place for a more stable civilization.*
Like the edges of the dwarf and troll civilizations, the shores of the giants' oceans, except that sea near the bottom, are filled with wights. However, using the preparations I've described below, giants are actually able to dive right into the ocean and fight off wights to hunt big fish and mammals underwater.
Giants' magic is shamanistic, in the sense that Wikipedia defines: "A practice that involves a practitioner reaching altered states of consciousness in order to encounter and interact with the spirit world and channel these transcendental energies into this world."
They use potions, made in collaboration with the spirit world: the shaman or shamans of any given tribe will make a number of neutral preparations, and then as part of the trance they enter (using some more rare, more difficult to make substance) they ask the spirit world to enchant the waters of the preparations. Thereafter, those preparations could be used by anyone to induce the trance-state and associated abilities that they contain, but they can't be created by someone who isn't on good terms with the spirit world.
Giants who use potion preparations their whole life over time take on spiritlike qualities. Extremely pale skin, sometimes to the point of paper-white or translucence, can occur, and if a person regularly uses trance potions to allow hunting spirits to inhabit them during puberty (as almost everyone in smaller giants' tribes do) they will tend to grow to between seven and nine feet tall.
Overexposure during this time period can eventually push a person beyond the veil: some giant tribes perform a kind of sacrifice, in which from seven years old on a child is kept in a trance state more often than not. They'll grow extremely skinny and tall, their skin will become translucent and their blood will become clear, and eventually they'll stop coming out of the trance, having become a permanent home for spirits. Many tribes believe that this sacrifice, performed at least once a generation, is necessary to keep the spirit world willing to cooperate. Anyway, no generation has passed without at least one tribe doing it.
*I mentioned earlier that there could be a more stable giant civilization along the river, and it occurred to me that the widespread use of potions and rituals is not sustainable in a more compartmentalized society like a city. This would probably result in a class separation, where, other than warriors and priests, citizens of the city-states of giant culture would look and live a lot more like all the other races in the world, and especially like most people in the globalized world of the setting's present-day, where a lot of people are not indoctrinated into their culture through a lifelong process of total immersion.
I alluded more directly in this post to variance than I did in the other ones, so this disclaimer may be less necessary, but I want to emphasize again that different groups of giant civilization differ, sometimes significantly, and that individuals within giants' society have independent identities, beliefs and experiences that are influenced by, but separate from, their civilization.