PSI

PSI (Psionics) or PK (Psychokinesis) refers to the psychic powers that appear throughout the Mother series. These abilities vary between their users, both protagonist characters and foes alike. PSI becomes stronger throughout the games, and the power level is designated by the Greek letters Alpha (α), Beta (β), Delta (δ), (Gamma [γ] in the unreleased English prototype of MOTHER and the Japanese versions of the trilogy),  Pi (π), Sigma (Σ) and Omega (Ω). Also, PSI abilities can be disambiguated into four different categories:

• Assist PSI -- Known for using shields, altering the status of an ally or foe (This doesn't include HP or PP), or inflicting a status ailment.
• Offense PSI -- Known for dealing significant, elemental, or even mortal damage to either ally or foe.
• Recover PSI -- Known to recover the HP and PP of an ally or foe, as well as removing status ailments, especially incapacitation.
• Other PSI -- Known for PSI used "only" in the overworld. Teleport is an example. (This is not applicable in Mother 3.)

PSI abilities come from the aliens of Giygas's species, though the secrets of PSI were stolen from them by George during the events of Mother. In EarthBound, various enemy types - humans, animals, aliens, and even inanimate objects - are able to use PSI, likely as a result of Giygas's influence. In Mother 3, the use of PSI/PK is generally limited to the Magypsies and their students, with rare exception. The Magypsies have apparently been using it for centuries, though it is worth noting that Mother 3 is said to take place in another world altogether from the first two games in the series.

Calling the offensive moves PSI was a translation error in EarthBound, as the attacks were called PK in the unreleased official translation of Mother.

Some PSI moves differ from game to game, and their description in a section will be what they do in that specific game.

PSI abilities in Mother

• 4th-D Slip -- Assist PSI, it is used to retreat with a 100% success rate. However, some battles can't be escaped, such as boss battles.
• BrainCyclone -- Assist PSI, it inflicts the "confused" status ailment to an opponent. This is a later level of BrainShock.
• BrainShock -- Assist PSI, it also inflicts "confused" to an opponent. 
• Darkness -- Assist PSI, it inflicts the "blind" status ailment to an opponent.
• DefenseDown -- Assist PSI, it slightly reduces the defense of an enemy. Later levels can target multiple foes.
• DefenseUp -- Assist PSI, it increases the defense of a party member by a percentage of their normal Defense. The later level can increase the defense of all party members.
• Healing -- Recover PSI, it heals a single status ailment from a party member. Later levels allow this ability to cure different status ailments from a party member.
• Hypnosis -- Assist PSI, it inflicts the "sleep" status ailment to an opponent. 
• LifeUp -- Recover PSI, it recovers the HP of a party member by an amount which increases with higher levels of the ability.
• OffenseUp -- Assist PSI, it increases the offense of a party member by a percentage of their normal Offense.
• PK Fire -- Offense PSI, an elemental ability that causes damage to all foes. A later level can OHKO all enemies.
• PK Freeze -- Offense PSI, an elemental ability that causes damage to one foe. Later levels can bring an enemy down to critical HP or target all foes.
• PK Thunder -- Offense PSI, an elemental ability that causes damage to one foe. Later levels can target all foes.  
• PowerShield -- Assist PSI, it can reflect any offensive PSI or attack at no damage to the user. This targets only one ally.
• PK Beam --Offense PSI, it is rumored to be the strongest attack PSI. Deals a significant amount of damage to one or all opponents and may even OHKO them. Resistance to this is impossible for your party to acquire, except for resistance to PK Beam γ, obtainable through the Franklin Badge, and any resistances the enemy may have are hidden when using the Check command. 

• PSI Block -- Assist PSI, it prevents an opponent from using any PSI.
• PSI Shield -- Assist PSI, it halves all damage. The later level can be used on all allies at once.
• PSI-Magnet -- Recover PSI, It steals 10 PP from one opponent.
• QuickUp -- Assist PSI, it increases the speed of a party member by a percentage of their normal Speed. 
• Shield Off -- Assist PSI, it removes any shield from one opponent.
• SuprHealing -- Recover PSI, it instantly revives a party member to full HP.
• Telepathy -- Other PSI, it has various uses on the field, usually to read minds or to talk with animals.
• Teleport -- Other PSI, it allows the user and his/her party members to teleport to previously-visited towns.

PSI abilities in EarthBound

• Brainshock -- Assist PSI, it inflicts the "strangeness" status ailment to an opponent. Can target one or more enemies.
• Defense down Assist PSI, it lowers the defense stat of an enemy to a low or high rate. Can target one or more enemies.
• Healing -- Recover PSI, it heals one or more status ailments from an ally. Some status ailments like "Mushroomization" can't be cured. Can be used outside battle.
• Hypnosis -- Assist PSI, it inflicts the "sleepiness" status ailment to an opponent. Can target one or all enemies in battle.
• Lifeup -- Recover PSI, it heals a party member to a minimum to maximum amount of HP. Can be used outside battle, and can target one or more allies.
• Offense up -- Assist PSI, it raises the attack stat of a party member to a low to high rate. Can be used for one or more allies.
• Paralysis -- Assist PSI, it inflicts the "numbness" status ailment to an opponent. Can target one or all enemies in battle.
• Shield -- Assist PSI, shields or counters most physical attacks. Effective when stacked. Can be used to one or all allies.
• Telepathy -- Exclusive PSI, it works like 'instant messaging' to another person. Paula uses this to communicate with Ness and Jeff.
• Teleport -- Other PSI, it can make the user "jump" into previously-visited towns. It increases walking speed, and is used only outside battle.
• PSI Farewell -- Exclusive PSI, works like Teleport β.
• PSI Fire -- Offense PSI, an elemental ability that can burn an opponent. Best against ice-based foes. Targets one row of enemies.
• PSI Flash -- Offense PSI, inflicts a random status ailment to an opponent. It can rarely incapacitate a target. Targets all enemies.
• PSI Freeze -- Offense PSI, an elemental ability that can freeze to an opponent. Best against fire-based enemies. Targets one.
• PSI Magnet -- Recover PSI, it steals a minimum amount of PP from enemy targets. Can target one or all.
• PSI Rockin -- one of the strongest Offense PSI abilities. Deals significant damage. Targets all enemies.
• PSI Shield -- Assist PSI, shields or counters most PSI attacks. Effective when stacked. Can be used to one or all allies.
• PSI Starstorm -- One of the strongest Offense PSI abilities. Deals major damage. Targets all enemies.
• PSI Thunder -- Offense PSI, an elemental ability that can inflict numbness, as well as very high damage. Targets a random opponent. Tends to miss often.

PSI abilities in Mother 3

• 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.

Unused dummy PSI - Mother 3 only

• PK Beta -- Poisons the entire party, only the unused Dung Beetle and Unworked Clay (the Dung Beetle that drops Silver Dragonflies) enemies has it and cannot be learned.
• PK Gamma -- Similiar to Paralysis except only the unused Tent Person and Unworked Clay enemies have and can use it, does not use any PP either even if PSI Magnet can suck the PP from Tent Person and/or Unworked Clay.
• PK Omega -- Only the unused enemies Snow Bunny and Unworked Clay have and can use this, works like Hypnosis and cannot be learned.