There are countless islands on the edge of the Sea of Chaos, varying dramatically in size, each with its own environment. These are constantly changing, but they change slowly; it can take anywhere from a day to a week for an island to shift from a barren desert to a verdant jungle. Weather is generally more dynamic, and often at odds with the environment; a vast desert can suddenly face a dramatic blizzard. The DM can use the tables in chapter 5 of the Dungeon Master’s Guide to determine weather, rolling again whenever it seems interesting to do so. Other tables in that chapter can also be quite useful for determining the chaotic content of an island; the Monuments and Weird Locales tables are a way to provide ideas for random discoveries, though the DM can adjust them to fit the story and the theme. Keep in mind that Kythri is home to mimics of all sizes; an unusual monument might be a colossal mimic!
The primary denizens of the Shifting Islands are monstrosities and beasts that blend the features of multiple creatures. Populations expand and contract, and don’t have to be sustainable, so adventurers could find a plateau filled with griffons, or a realm of chimeras where each one has a different arrangement of heads. The intelligent inhabitants of the island are almost entirely slaadi, but they aren’t necessarily hostile. The Slaad Cultures table earlier in this section can give ideas about their motives, and the Random Settlements tables in chapter 5 of the Dungeon Master’s Guide can generate a random slaad community. The Race Relations tables could refer to the different colors of slaadi, or to their relations to intelligent monstrosities or planar travelers; the “racial minority are rulers” result could be a slaad village where adventurers are worshiped as gods!