The Astrologian is a primarily a support-based job. Stat-wise, it has high MP and decent Intelligence, but is slow and fragile. Its Astral Magic provides a variety of stat boosts and beneficial effects, which--in the right hands--can turn the tide of battle.
Prescience saves Astrologians by allowing Astral Magic to go first despite their poor speed. Early on, Astrologians aren't very exciting, but their abilities eventually become essential, especially when combined with Spellcraft to affect the whole party.
Spells and abilities that boost stats or provide supportive effects trigger at the beginning of the turn.
Astrologians are naturally slow, so this ability gives them a huge helping hand to unleash their buffs before other allies--and enemies--have time to act.
Level 1: Astral Magic Level 1
Physical Boon increases a character's Physical Attack by 30% for 4 turns (up to 150%), while Mystic Boon increases Magical Attack by 30% instead. Useful for denting bulky foes or racking up more damage. Gets better when you can combine it with the Blast or Mist Spellcraft.
Level 2: Astral Magic Level 2
Evade Boon increases a character's Evade by 30% for 4 turns (up to 150%). A decent option when facing physical foes, before you get spells that boost defences.
Elemental Ward creates a barrier around a character that halves damage from a chosen element for 4 turns. Cannot be extended by Spellcraft. Makes foes that rely on elemental attacks far easier to handle. Again, it's more useful when you can apply it to your party with Spellcraft.
Level 3: Precognition
Highly recommended so enemy mobs never gain a surprise advantage during battle. Especially later on, when enemy mobs can easily savage your party before you get a chance to retaliate.
Level 4: Astral Magic Level 3
Speed Boon increases a character's Speed by 30% for 4 turns (up to 150%). Speed is important as it determines the order in which characters act. Handy for catching up with faster foes or consistently outrunning foes with similar speed.
Magic Mirror creates a barrier around a character that reflects White Magic, Black Magic, Time Magic, Spirit Magic, Holy Magic and Astral Magic for 4 turns. Cannot be extended by Spellcraft; duration is doubled with Good Measure.
This is the same as the White Mage's Reflect in Bravely Default, allowing characters to bounce back most forms of magic. Since White Magic and Holy Magic are reflected, you'll need to use items or other methods to heal. Can be cast on enemies to stop them healing.
Level 5: Astral Magic Level 4
Physical Ward increases a character's Physical Defence by 30% for 4 turns (up to 150%), while Mystic Ward increases Magical Defence by 30% instead. Can be a life-saver when dealing with bosses that hit like a truck. Combine with Blast or Mist Spellcraft for best results.
Level 6: Prescience
Now that you're free to equip Prescience in any job, there are dozens of possibilities. Of note, it's fantastic when combined with the Exorcist's Undo Action, Time Mage's Re-raise, Guardian's Soul Mirror or Templar's Rampart.
Level 7: Astral Magic Level 5
|Command||Lucky Day: 5 MP Elemental Mirror: 12 MP|
Lucky Day boosts a character's success rate with abilities that have a chance of failure or try to inflict a status ailment for 4 turns. Most bosses are immune to or resist ailments, so this is mainly useful for tripping up enemy mobs.
Elemental Mirror creates a barrier around a character that reflects physical attacks of a chosen element for 4 turns. Cannot be extended by Spellcraft; duration is doubled with Good Measure. Hilarious against enemies that rely on physical elemental attacks. So long as they don't absorb their own element.
Level 8: Astral Magic Level 6
|Command||Elemental Boon: 24 MP Elemental Barrier: 36 MP|
Elemental Boon increases a character's elemental damage by 1.5 times for 5 turns. Cannot be extended by Spellcraft. 50% more damage is fantastic, so if you're using elemental attacks, you'd be silly not to use this.
Elemental Barrier, meanwhile, creates a barrier around a character that nullifies elemental damage for 4 turns. Cannot be extended by Spellcraft. Enemies that rely on elemental attacks can be more or less trivialised with this.
Level 9: Prolong Support
As long as one person has Prolong Support, your entire party will retain their stat boosts for double the number of turns. Keep in mind that this applies strictly to stat boosts, not supportive boosts like elemental nullification. Otherwise it's not a bad ability to hang onto.
Level 10: Limit Breaker
Limit Breaker is beyond impressive. For example, the maximum Physical Attack boost you can receive normally is 50% (for a total of 150% Physical Attack). With Limit Breaker, you can receive an additional 50% boost (for a total of 200%).
With double the buffs, you'll be hitting for amazing damage and tanking hits like you couldn't imagine. Of course, it takes a while to setup and is sadly vulnerable to Dispel. Otherwise, you can combine it with the Fencer's Bloody Wolf or other moves that instantly maximise stats.
Level 11: Astral Magic Level 7
Status Barrier creates a barrier around a character that nullifies status ailments. It doesn't sound too fancy, until you come across late-game bosses that love to spam tricky ailments. Use it in conjunction with the Black Mage's Group-Cast All for optimal efficiency.
By the way, Status Barrier also prevents the annoying Love and Freeze ailments, so you'll definitely want to have it when facing the Ba'als that inflict those.