MP
MP, or magic points, are required to cast spells and use certain magical abilities. If the MP cost of a spell is greater than your remaining MP, you cannot cast that spell. MP slowly regenerates over time in and out of combat.
MP formerly varied based on Piety, much like HP does with Vitality. As of Patch 5.0 (Shadowbringers), the MP cap for all levels was changed to 10,000, and MP costs for all actions became fixed values.
All Disciples of Magic (
Magical Ranged DPS and 
Healer) have actions that require MP. Additionally, two 
Tank Jobs also have actions utilizing MP: 
Paladin and 
Dark Knight. For the tanks, spells are scaled on strength rather than intelligence or mind.
Consumables
Resurrection spells are very taxing on the caster's MP reserves. In addition, the KOed player is only revived wtih 20% of their maximum MP, meaning consumables can be useful to them as well.
| Item | Effect |  HQ Effect
|
Source |
|---|---|---|---|
 Ether |
Restores up to 6% of MP (600 points max). | Restores up to 8% of MP (800 points max). | Purchase from Vendors for  60 gil, Crafted by Alchemist, or from Quests
|
 Hi-Ether |
Restores up to 7% of MP (700 points max). | Restores up to 9% of MP (900 points max). | Purchase from Vendors for 432 gil, Crafted by Alchemist, or from Quests
|
 Mega-Ether |
Restores up to 8% of MP (800 points max). | Restores up to 10% of MP (1000 points max). | Purchase from Vendors for 792 gil or Crafted by Alchemist
|
 X-Ether |
Restores up to 10% of MP (1000 points max). | Restores up to 12% of MP (1200 points max). | Purchase from Vendors for 1,108 gil, Crafted by Alchemist, from Duties, or from Quests
|
 Max-Ether |
Restores up to 12% of MP (1200 points max). | Restores up to 15% of MP (1500 points max). | Crafted by Alchemist or from Quests |
 Super-Ether |
Restores up to 14% of MP (1400 points max). | Restores up to 18% of MP (1800 points max). | Crafted by Alchemist or from Quests |