Obsidian and Stygian

Obsidian noun - Acid or granitic glass formed by the rapid cooling of lava without crystallization; usually dark, but transparent in thin pieces.

Stygian and obsidian are semantically related in black topic. In some cases you can use "Stygian" instead an adjective "Obsidian", when it comes to topics like dark.

Stygian adjective - Being without light or without much light.

Obsidian and stygian are semantically related in black topic. Sometimes you can use "Obsidian" instead an adjective "Stygian", if it concerns topics such as dark.