An overview of the Radiant Ruins biome, added with the Take Flight update.
Source: http://www.shapestonejournal.net/radiant-ruins-guide/
Take to the skies! The Radiant Ruins is a biome added in the Take Flight update, and is located on its own map.
Once the stronghold of the mighty Sun Goddess, this blasted realm now hides the secrets of the Elysians … along with a healthy compliment of traps. Venture into this world through a special portal and gather new treasures to aid you in your journeys.
GETTING THERE
To get there, use a Sky Portal. They are only placeable in Club Worlds, and can only be used by members of that club world. They can be crafted at the Crafting Bench for 2000 Infinium, 500 Faerie Dust, and 500 Bottles. It's also possible to be invited to a Radiant Ruins map or to join one through a friend on your friend's list.
Don't bother going to Radiant Ruins unless you have a set of wings (obtained by reaching Mastery rank 20). You won't be able to do anything without them.
GLIDING
The Take Flight update introduced gliding, a new mechanic in Trove. While gliding is available everywhere, Radiant Ruins is designed specifically for gliding. The biome is made up of floating islands and chunks of land. It is possible to fall to your death, so be cautious.
To activate your wings, press and hold spacebar while your character is airborne (press once to jump, then press and hold once more to use your wings). You don't need to hold your spacebar down to continue gliding, but any kind of action (jumping, attacking, etc.) will cancel your glide and send you plummeting. Pressing forward while gliding makes you dive, increasing your speed considerably but also causing you to lose altitude quickly. Pressing back while gliding slows you down but causes you to lose altitude less rapidly.
Passing over updrafts (pictured above) while gliding will send you high into the sky. Hold back (S) to maximize the amount of life you get from an updraft.
ENEMIES
Radiant Giants (also known as Sky Giants) are the only mobs currently in Radiant Ruins. They drop Radiant Shards and an item of at least Legendary (orange) quality when killed. Radiant Giants also have a chance to drop a Radiant Cache, which can contain blank scrolls, Radiant Shards, and the Radiant Steed. Players regularly form Sky Giant farming groups to kill these mobs more quickly and efficiently.
DUNGEONS AND QUESTS
The only dungeon/quest currently available in Radiant Ruins is the Dark Heart, which is kind of like a timed target-practice event. When the Dark heart is activated, you have 45 seconds to destroy as many Radiant Shard boxes as possible. Each box drops a single Radiant Shard, which you get to keep after the completion of the quest. Radiant Shard boxes also have a chance to drop Radiant Caches.
RESOURCES
There are two kinds of resources unique to Radiant Ruins. Crystalized Cloud (which has a chance to drop the Nimbus Cloud mount) can be mined like normal ore and is used in the Runecrafting profession. Radiant Shards, mentioned above, are obtained through the Dark Heart dungeon/quest and are also used in Runecrafting.