Stygium

Styx mite blocks and stygium crystals spawn in the nether interspersed with netherack (mite blocks in large clumps, crystals individually)stygian glass makes up a part of some (currently nonexistent) structures in the nether.

Styx mite blocks look like netherack with black and green circles in it, acts like silverfish stone but releases a styx mite instead of a silverfish. Styx mites act like 1x1 spiders with high health unless otherwise said.

They spit styx glue, which slows your movement and weakens your attacks, if you walk into an area with a light level of 13 or higher (or just set yourself on fire), it will stop the effect, but also set you on fire. Styx mites will attack like spiders if you're already glued, and will not shoot glue at a glued/on fire player.

All styx mites have an invisible anger meter that goes down over time, it starts at 5, the higher the meter is, the more damage it does, and the faster it gets. Damaging it will make meter go up. High light levels/being on fire will not damage it, but will also cause the meter to go up.

At six it will occasionally set fire to the block it's standing on. At nine, it will set fire to other nearby blocks, at twelve, it will break nearby styx mite blocks, at sixteen it will regenerate, and at 23 it will explode, setting fire to nearby blocks. When its anger level is low, it looks like a giant silverfish with spider eyes and legs, but when it gets angry, cracks start to appear in its shell, at first they are the same shade of red as the eyes, but as it gets angrier, the cracks spread, and then both the cracks and the eyes change to orange, then yellow, then white, and then for one second before it gets so angry that it explodes, the shell glows yellow and white, and the cracks/eyes (they are indistinguishable at this point) glow neon blue.

Drops:stygium shards (can be used to craft stygium crystals/stygian glass, if cooked in a furnace, the furnace will explode) and spider eyes.

Stygium crystals are black in low light levels, glow in medium light levels, and explode if they're exposed to high light levels, if they're mined in medium light levels, if they are broken by explosions, or if they're set on fire. They can be crafted out of nine stygium shards.

Making a 3x3 square of stygium crystals with four wither skeleton skulls facing away from the middle on top should cause styx mites to spawn on the middle block of stygium crystal once every few minutes if there is a player nearby (these can be found in the same (currently nonexistent) structure as stygian glass).

If you build a beacon pyramid out of stygium crystals and put a eye of ender in the beacon, the beacon will turn black and nights in the area will become more dangerous, more monsters will spawn, some with permanent status effects, and some new ones will spawn, with unique drops.

A final use for it would be: if you build a nether portal-like structure out of it with a mob head on it then activating (with sunlight) two with the same mob head should enable you to travel between them as if using a nether portal, if there are more than two with the same head, you will travel to a random one.

Stygian glass is a mostly decorative block that can be mined with a stone pickaxe, and is opaque in low light levels while being transparent in higher ones. It can be crafted with four stygium shards and a block of glass.