The Uvite Islands are the third Twilight Dimension. In this dimension, almost every mob is automatically hostile. It is recommended to have a decent set of armor for the Uvite Islands.
To get to the Uvite Islands, you will need 90 Azurite Fragments to create 10 Azurite Blocks. Then, you place down the blocks similarly to a Nether Portal. Then, you light the portal with a Twilight Clock and enter.
Although it is less likely than the other dimensions it is recommended to still bring blocks in case you spawn in mid-air. Before entering you need to decide on what you will do. Are you going to hunt the mobs for Uvite Souls or avoid them all and just mine the fragments.
The Uvite Dimension represents sunset, meaning it is semi-dark in the Uvite Islands. If you light the place up, you will see that everything is purple. Uvite Ore can be seen in the dark, and it is the exact same as previous ores: It is purple, the color of its dimension, and it drops Uvite Fragments when mined. The Uvite Islands is also the waypoint between peaceful and agressive, just like sunset, which is the transition from day to night. The Uvite Islands aren't meant to be very dangerous, they are just meant to prepare you for the later dimensions, which are far more challenging.