Advanced Magic Master

Answer the question to: What does Advanced Magic, Alephan's Wisdom and Advanced Magic Master actually do?
Correcting the mis-translation of these skills.

Scholar's and their mastery of magic

The original translation for Advanced Magic (15 SP), Alephan's Wisdom (30 SP + 3BP) and the Advanced Magic Master passive ability is poor, as they all fail to properly describe what they actually do. Here are corrected translations based on observed effects in game:


Advanced Magic - selected AOE spells are upgraded to Tier 2 potency for 2-5 turns depending on amount of BP spent.


Alephan's Wisdom - selected AOE spells are upgraded to Tier 3 potency for 3 turns. Overwrites Advanced Magic if the subject was under it's effects.

Advanced Magic Mastery - the duration for Advanced Magic and Alephan's Wisdom spells are extended by 1 turn for no extra cost. Advanced Magic becomes 3-6 turns depending on BP expenditure; Alephan's Wisdom becomes 4 turns. Both images show the skill icon with the Advanced Magic Mastery passive selected.

Which spells benefit

Cleric
Heal Wounds -> Heal More -> Heavenly Healing
Luminescence -> Radiance -> Lux Congerere
Revive -> Revive & Restore -> Revive & Rejuvenate

Arcanist
Malice -> Resentment -> Malevolence
Blessing -> Benediction -> Spiritual Grace
Hex -> Curse -> Scourge

Scholar
Fireball -> Firestorm -> Ignis Ardere
Icewind -> Blizzard -> Glacis Claudere
Lightning Bolt -> Lightning Blast -> Tonitrus Canere
One True Magic -> One True Magic II -> One True Magic III (Osvald only skill)

In all cases the cost is unaltered. In comparison to the first game where the price for a multi-strike spell was generally: 8 SP per attack plus a 6 SP recast fee.

For attack spells, tier 2 = 2 hits, tier 3 = 3 hits. The damage per strike diminishes with each tier increase; i.e. tier 3 deals the least damage per strike. However, the total damage dealt improves with each increase in tier. [segment corrected in line with comment below].
For healing spells, the potency is upped.
For Hex the base duration is +1 for tier 2, +2 for tier 3.
If Osvald chooses to use his latent power (focused damage), the enhanced AOE attack spells are capable of being focused on a single target. Prepare for a potential of 3 lots of 9,999+ damage per hit on the target. Save this for bosses with broken shields.

Which spells DON'T benefit

Merchant
Ember

Apothecary
Icicle
Healing Touch

Hunter
Thunderbird

Cleric
Holy Light

Dancer
Sweeping Gale
Windy Refrain - Agnea only skill.
Agnea's ability is ignored even though it is an AOE spell; no reasoning as to why - it is an AOE magic attack with a perk, much like the Arcanist.
Agnea's passive ability to turn a single target effect into a party effect can't bypass the rules governing the benefits.

Thief
Darkest Night
Veil of Darkness - Throne only skill
Throne's ability is ignored even though it is an AOE spell; no reasoning as to why - it is an AOE magic attack with a perk, much like the Arcanist..

Scholar
Elemental Barrage

Notes:
1) No single target spells receive any benefit, limiting the gains to Scholar's, Cleric's & Arcanists spell sets. This makes Osvald & Temenos the prime candiates to be boosted.
2) The names for the basic three strike skills are the exact same as those of the Sorcerer job in the original octopath traveller. Dark was Tenebrae Operiere, Wind was Ventus Saltare. Malevolence substitutes for Tenebrae Operiere.
3) Wind is the only element that lacks a multi-strike AOE spell, as Windy Refrain can't be boosted and no job has a wind AOE spell.
4) This guide was inspired by a curiosity as to how the Arcanist had 3 tiers of ability listed on some guides without a clear indicator as to how to access those tiers.

[Reynard-Miri]

A small correction: it is not number of turns, it is number of casts. If you spend a turn doing something other than casting one of these spells, the number does not decrease.

[abaoabao2010]

Correction for this line: "For attack spells, tier 2 = 2 hits, tier 3 = 3 hits. The damage per strike is unaltered, as this is a frequency not an intensity improvement for offensive spells."

The damage IS lowered at higher tier. It still does more total damage and is better at breaking weakpoints, but it's not nearly as good as you're saying.

Comparing the damage of fireball, firestorm and ignis ardere at 3BP:
Fireball: 3.89
Firestorm: 2.94, 2 hits. Total is 5.88.
Ignis Ardere: 2.52, 3 hits. Total is 7.56.

Ability data's all gathered in the community spreadsheet:
https://docs.google.com/spreadsheets/d/1vd0ZS8QmKC14qlXw43jPm0ytzMy4nczKJG5CD5QSi3M/edit#gid=18404082