Risia, the Plain of Ice, is named such because that's mostly what it contains. Almost every layer is blanketed in snow and ice, some with blizzards and others that are eerily calm and silent, but all of them contain seemingly endless, frozen wastelands. It would be simple to say that Risia is the plane of ice, but much like with Fernia, this is an oversimplification. Natural ice is represented in Lamannia, which has artic regions and natural blizzards. Risia is more than ice itself, it represents the ideas that the cold evokes in mortals; The utter stillness that confirms we are truly alone, nothing changing, everything staying the same for all eternity, preserved within the ice.
Risia is dangerously cold, and creatures that aren't adapted to cold environments (or wearing really big coats) are likely to succumb to the cold. It's so cold that even magical fires struggle to exist in Risia, and spells that weaponize the cold are more powerful. Perhaps the most interesting properties of the plane, however, are those related to stagnation and preservation.
Though time passes consistently with the Material Plane in Risia, creatures don't age and they don't grow, they remain exactly as they were when they arrived in the plane. Similarly, wounds don't heal naturally, though unlike in the Mournland, magical healing is still effective. Risia also preserves the creatures that reside there, placing them into a state of suspended animation when they would otherwise die, and encasing them in the ice. Strangely, dwarves seem to be immune to these properties of the plane, and they can age, have children, and die in Risia, just as they would on the Material Plane.
There aren't many creatures in Risia, it would be antithetical for a plane defined by isolation, and you could travel for days without seeing a single living thing. That said, explorers who travel to the plane often report that there is a sense of a presence watching them, and they often claim to somehow know that this presence means them harm. It's entirely possible that the isolation, and the stagnant nature of the environment, was simply getting to them, though.
Each of the Giant civilisations in Xen'drik had different specialties, and the Group of Eleven studied most of the planes. When the doom came for them in the wake of their war with Dal Quor , the arcanist dedicated to the study of Risia, alongside her magebred children, fled to the plane she had studied all of her life. Nothing changes in Risia, so it's possible that these giants are still there, still alive.