BetterNether

Use a bucket of Water on a Lava-Source above Soulsand/-stone to generate blue Obsidian.

Use a Lightning Rod to create crying (or weeping) obsidian.

Some of the new Nether Biomes (rendered using Iris and Complementary Reimagined)

All Nether Pickaxes have improved mining speed for Obsidian Blocks

All Full Obsidian related Blocks can be used as a portal Frame. Other mods can add new Frame-Blocks using the custom Tag *c:nether_pframe*

Build arbitrary shaped nether portals, with all the previously enabled Obsidian Block