With the Nether update coming up, I have an idea for a new ‘beach’ biome. This would be on the borders of lava lakes. The main blocks would be obsidian sand, which can only be dug up with an iron shovel. It can be smelted into black glass which is highly durable. On the beach there are twisted spires of obsidian blocks. A new mob spawns on this beach.
The Spark is a small, floating mob that has 5 health and does 3 damage plus burning. It is fast and hard to hit, and has the appearance of a bubble of lava with the bottom encrusted by obsidian with small obsidian legs and large obsidian claws in the front, and red eyes. Killing it causes a small, fiery explosion.