Underground Conduit

The crafting recipe is similar to the underwater conduit with a Soul of the Earth (found in the deep dark biome - could be what the Warden is protecting) and 8 amethyst crystals surrounding it. Benefits would be night vision, haste 1, and slow falling. Another benefit could be that it would make lava semi-transparent, enough so that you could clearly see the lava but also see the blocks under it. The blocks needed to surround it to activate it would be copper blocks.

The specific details could be changed but I think the basic idea of a conduit underground would be a good idea. I also think it would add something useful as a reward for surviving the Warden.