PSI

PSI, or PK in the Super Smash Bros. series, is a major mechanic in the series.

Origin and discovery
PSI was originally used by Giygas's race. When George and Maria were abducted by these aliens in 1909, George studied the powers and eventually learned to use them and eventually passed them down to Ninten, his great-grandson. Much later, it was shown that in the year 199X, Ness, Paula, and Poo could each use different types of PSI.

Types of PSI
Each PSI move can have up to 5 ranks, α, β, γ, Σ, and Ω (Also π in Mother).

There are also three categories of PSI: Assist, Offense, Recover, and Other.