Whenever I host a world without a caves, I am able to equip the krampus sack, skinned as the void bag, and hear the sound the void bag makes in Terraria when you use it. But, when I try this on a server with caves enabled, it just makes the same sound when equipping a normal krampus sack. I am curious if others can confirm this too, just to know that it isn't only on my end. I know that other Terraria items, such as the Terraprisma and the Paint Brush, make a Terraria related sound effect in both scenarios, so I am not sure what happened with the void bag.
1. Start a server with no caves enabled
2. Reskin a krampus sack with the void bag skin (this step requires owning the skin)
3. Listen to what sound it makes when you open (if previously closed) or equip the krampus sack
4. Start a server with caves enabled
5. Repeat steps 2 and 3
6. Compare the sounds and notice a difference