You can find the Polyatomic Ion Particle only in the Fortress Region in The First Descendant. Moreover, they can only be obtained as a drop for eliminating boss monsters.

Polyatomic Ion Particles can only be found in the Fortress Region. To get them, you need to participate in missions and kill enemies with yellow health bars (aka boss monsters).

A polyatomic ion that was thus far inaccessible with conventional mass spectroscopy has now been uncovered using extremely short laser pulses. Catching a glimpse of this ion would open up new ...