All of my larger scale maps have deserts in them, and even the smaller scale maps have serious deserts signposted, somewhere just off the map edge.
Deserts give us both the opportunity for all the good old RPG tropes - nomads, Egyptians, pyramids, mummies - and a blank canvas where all manner of oddities can exist, and, face it, party travel through an almost featureless landscape does have some advantages and some issues.
Here is a list I started quite a while ago, inspired by an old National Geographic documentary and added to when inspiration struck. They are events, places, or oddities that may exist in the deserts. Some have secrets or dangers, and they can be simple diversions to note while hurrying to accomplish another task, or be the starting point of something entirely new.
12 Places of Note, as recorded by Induwar of Khallis
1. A valley in a deserted wasteland, where green glowing liquid seeps from the ground and supports a forest of 3-5m high carbonate tubes that contain longer red feathered 'worms'. These worms have their 'roots' in the ground, absorbing the liquid and jaws that catch the brightly coloured flying lizards that abound.
Reasonably safe for travellers, as wild beasts and civilised groups tend to avoid this area, but prolonged exposure to the liquid can cause mutations, and magic is very unstable in its presence.
Inspired by this
2. Shifting sandstorm that is the only entrance to The Jewelled City of Dreams. Ancient and cursed, it sleeps for now, but undoubtedly holds perils, treasures and answers.
3. Shallow acid or alkaline lakes, where rare rainstorms drain into a basin with no outflow. The water evaporates, leaving behind thick expanses of salt on the edge, stretching for miles. The water is sickenly salty and burns if drunk. It can be an important place for nomad salt harvesting, or a nesting place for naturalised birds or flying lizards, which may be hunting, fleeing or have a cute baby stuck in the salts.
4. Giant pyramidal dunes of sand, difficult to travel over. However, the base of one has a perfectly round 1.5m wide tunnel vanishing into it. Inspection shows that it is lined with silk-like matting, and very sound. The network of tunnels within the dunes can save days of hot and tiring walking, but the White Lady, the magically disguised spider-demon that creates these tunnels, may be encountered in her central lair.
5. A line of palm trees stretching into the distance in the flat sandy wasteland. Standing every 100m or so apart, sometimes with a clump of two or three trees, but usually only one. These mark an underground spring, and 5-10m of digging will reach mud. The dates of the trees can stave off hunger and starvation, but be wary of the ferocious nomad lizard riders, who claim the trees as their own.
6. A small spring in a rocky wasteland. No vegetation other than a small scrubby shrub, with large yam-like tubers. These are the only food source for a very long way, and although they are indigestible when raw, when cooked they become delicious, nutritious and a potent hallucinogen. Fun for everybody!
7. The Fata Morgana - a vision of Cyclopean ruins, a giant statue or a cliffside palace, floating mirage-like above the horizon. What and where is this place, and what treasure does it hold, if it exists at all? Perhaps the only path to reach this place is to climb into the mirage, as it exists out of time and space...
8. A sandy dunefield, with thousands of limestone pinnacles rising up to 5m high. From a distance they resemble the ruins of a vast city but closer they are recognisable as bizarre but natural formations. Some contain the dwelling places of small, goblin-like animals, that although uncivilised, can use powers of illusion to misdirect trespassers. If that doesn't work, they fling their faeces at intruders.
9. A vast thicket of Saguaro like cacti with narrow animal paths the only sane entrance. There are packrats, a surprising number of small birds and many venomous spiders, snakes and lizards infesting the forest, but it will probably be the half ruined tower jutting out of the centre of the forest that attracts the traveller. This leads to an underground cavern made nearly impassable by the thickets of cacti roots reaching through to the subterranean water present. Beware the fungi thickets and the clone farmers, but especially their master, who once inhabited the tower.
11. A number of straight sided stone monoliths, up to 500m high and flat-topped, rising from the arid gravel desert surface. Many of these monoliths have lush green rainforests growing on top, with vines and ferns cascading down the top part of the walls. Brightly coloured birds circle overhead. Who or what created and sustains these amazing features? And how does one reach them? Did I mention the strong anti-magic field around them?
12. A series of large, complicated glyphs carved into sandstone walls or even scratched into the desert skin. The largest is 10m high, and no sign of their meaning or origin remains. Certain mages, steeped in ancient and bizarre lore, may recognise them as fragments of the arcane alphabet that all spells are written in, although they make no sense now.