Demonic Pumpkin

This would look like a Jack 'o Lantern, but the carvings would be glowing red and the body would be black instead of orange. 

It would be crafted with a carved pumpkin, four ghast tears, and four blaze powders. Alternatively, it could also be found at Piglin camps, in Nether chests, and in abandoned zombie villages in the overworld. 

The purpose would be the opposite of a typical light-source, rather than reducing mob spawn-rates, it would increase them. You could place demonic pumpkins next to spawners in order to not only gain a light source but to increase the frequency of mobs spawning for XP-farming.

It would be somewhat difficult to obtain but not impossible and would be rewarding for the player. It would give an extra reason to hunt for Blazes and would give the somewhat rare ghast tears an extra use. It would also give the players more choice on how they gather XP.

It would take the same amount of time to mine as a regular carved pumpkin, and breaking it would just give you the block back. 

It can't be used in typical pumpkin crafting recipes.

It would also look very cool as a light-source and building block. Many haunted houses or other spooky builds would benefit greatly from it.

Thank you for reading my suggestion.