How to obtain Phase Matter?

[Late]

I need Phase Matter for this guy who gives the key things for the vaults.

[MysticMalevolence]

It comes from ghost-like mobs, generally the ones that phase through walls.
Not the erchius ghost. It doesn't die.

[Late]

Where can I find these creatures again?

[MysticMalevolence]

Forest and midnight planets, Snow and Tundra planets, above planets in the asteroid layer, probably a few more.

[Late]

Gracias

[Meme Lord Stranger]

They also appear in sub-biomes of Forest and Lush planets but I can't remember which ones specifically

[Late]

Ah ok