Spectral

Spectral is a mod that currently adds 3 items, pictured below:

The first, Spectral Dust, is crafted from phantom membranes and can either be eaten to turn temporarily spectral, or put onto a mob to turn it spectral.

The second, Spectral Goggles, put who wears them to enter a spectral state, allowing them to see and interact with spectral blocks and entities. These goggles can be crafted with Spectral Blocks, Spectral Dust, String, and Iron ingots.

The third, Spectral Block can be placed down as a normal block, but can only be seen, collided with, and broken by spectral players and mobs. (This function is per-player, so you might be able to see spectral blocks while your friends cannot!) This block can be crafted from Spectral Dust and glass!

Mechanics

The basic mechanics of Spectral function as such: There are two states living entities can be in, either normal (non-spectral) or spectral. This depends on their spectral_vision attribute (0 for normal, 1 for spectral). A non-spectral entity cannot see, hit, or push spectral entities, and it cannot break, collide, or see spectral blocks. Spectral entities cannot see, hit, or push non-spectral entities, but can fully interact with other spectral entities and spectral blocks.