INVS element is simple enough. It's a blue solid that, when exposed to > 4 pressure, or < -4 pressure, essentially opens up and allows other elements to pass through it.

Once pressured or vacuumed, elements will lose their collision with one another in addition to passing into the INVS. This effectively makes it possible to store an infinite amount of mass inside of an INVS block.

...However, INVS is not like Ehole. Particles passing through INVS are not prevented from falling right back out, so care should be taken. Elements will drop out of INVS and resume having collision and mass once outside.

Due to the fact that INVS conducts heat, GOL or other element combinations can be used to heat it, where under pressure other elements will pass through it and absorb this heated temperature. This is a comically efficient way of heating matter that can heat any amount of particles at once.

..The animation has low quality color. The only view that showed them going through was fire >_>; Notice how the salt turns to lava while passing through.

Finally, INVS can be used as a photon gun cap that turns any PHOT passing through into NEUT. It can be used to make neutron lasers, effectively.