PSI

PSI means Psionics and has been carried through the game for Lucas, Kumatora, The Masked Man and even some enemies and bosses. The PSI can ONLY be used if the character has enough PP (Psychic Points). Any characters that can use PSI can inflict more damage than regular hitting and weapon usage. There are three categories of PSI that can be unlocked.

Offense

Assist

Recover

Different PSI Abilities

• Brainshock -- Assist PSI, it inflicts "strangeness" to one or more opponents.
• Counter -- Assist PSI, it reflects 50% of physical damage from an opponent. Some attacks can't be halved, however. Can be used to one or more allies.
• Defense Down -- Assist PSI, it lowers the defense stat of one or more opponents at a minimum to a maximum rate. Effective when stacked.
• Defense Up -- Assist PSI, it increases the defense stat of one or more allies by a low to high rate. Effective when stacked.
• Healing -- Recover PSI, it removes one or more status ailments to one or more allies.
• Hypnosis -- Assist PSI, it inflicts "sleepiness" to one or more opponents.
• Lifeup -- Recover PSI, it recovers the HP of one or more allies to a range of minimum to maximum rate.
• Offense Down -- Assist PSI, it lowers the attack stat of one or more opponents at a minimum to a maximum rate. Effective when stacked.
• Offense Up Assist PSI, it increases the attack stat of one or more allies at a minimum to a maximum rate. Effective when stacked.
• Paralysis -- Assist PSI, it inflicts "numbness" to one or more opponents.
• PK Fire -- Offense PSI, an elemental attack that can target a row of enemies. It rarely inflicts the "burn" status ailment. Effective against ice-type foes.
• PK Flash -- Offense PSI, it can inflict a random status ailment to each of the enemies in battle. It has a low chance of incapacitating a target.
• PK Freeze -- Offense PSI, an elemental attack that can target one opponent. It rarely inflicts the "freeze" status ailment. Effective against fire-type foes.
• PK Ground -- Offense PSI, it targets all enemies in battle. Damage is low, but repetitive. It has a low chance of "tripping (solidification)" to an opponent.
• PK Love -- One of the strongest Offense PSI abilities. Deals significant damage to all opponents.
• PK Starstorm -- One of the strongest Offense PSI abilities. Deals major damage to all opponents.
• PK Thunder -- Offense PSI, an elemental attack that can randomly attack any opponent. Tends to miss often, and rarely inflicts the "numbness" status ailment. Effective against mechanical-based enemies.
• PSI Magnet -- Recover PSI, it steals a low amount of PP from an opponent, to recover the user's PP.
• PSI Counter -- Assist PSI, it reflects 50% of PSI damage from an opponent. Some attacks can't be halved, however. Can be used to one or more allies.
• PSI Shield -- Assist PSI, it reduces PSI damage from an opponent by 50%. Some attacks can't be halved, however. Can be used to one or more allies.
• Refresh -- Recover PSI, it recovers a minimum to a moderate amount of HP to all allies. Effect disappears in a few turns.
• Shield -- Assist PSI, it reduces physical damage from an opponent by 50%. Some attacks can't be halved, however. Can be used to one or more allies.

Credit to EarthBound Wiki for this information.