While
@sonicyoash and
@Kratos1990 covered the Tonberry senses and drops well, I want to bring up some of the more unconventional things the Tonberry had to offer, as some of what I found was not from a creature you can obtain in the CM list. If this stuff cannot be obtained because of your ruling
@zagan, that's fine, I just wanted to bring these up for more options.
There was an enemy in FF6 called
Tonberries, pretty much just a group of them together, but they dropped the best spellcasting armor in the game for female characters, the
Minerva Bustier, not much use to Alex but can still be worn by an ally like his other Protectorate members or partners, or it can be given for study on how it can block elemental effects.
The
Tonberry (Final Fantasy IX) has some neat drops too, the
Phoenix Pinion can be used to revive a person like the Phoenix Down, though only during battle, and can be used to auto summon Phoenix whenever you're about to die, which hasn't much use now but would be great if the rolls do land on Phoenix one day. This Tonberry also drops
Peridots, this one is a support item for Ramuh that increases the damage his Judgement Bolt does when summoned, again useless now but could be a boon to stock if he ever gets rolled and can be used as a healing item that scales with the number of Peridots you have x68.
FF XIII-2
Tonberry gave
Hermes Sandals, which grant Critical: Haste and Low HP: Power Surge when HP is Critical and below 30% HP respectively. a nice addition to Alex's set Contingent Summoning of
Fluff when critically injured.
In FF XV this
Tonberry drops the
White Choker, an accessory that slightly increases HP recovery rates.
The Type 0
Tonberry drops Anima Lanterns, which is described as a lantern that governs life and death that grants
Reraise along with a few seconds of
Invincibility after being revived.
While there are two versions of Tonberry's that are summons, they weren't entries on the CM list. The one from FF VIII requires a fight with the King Tonberry to gain the Guardian Force
Tonberry (Final Fantasy VIII summon), while Crisis Core needed you to have the Tonberry Knife, called the Chef's Knife they wield, for the
Digital Mind Wave to call forth its
Murderous Thrust attack. DMW is the Limit Break system in that game, a lottery reel which is randomly affected by Zack's mentality and emotions as of the current story progression, and you would have to hope it rolls for Tonberry in
Chocobo Mode, the Creature Summon reel for those who are still able to understand what I'm saying and not totally confused. Unfortunately, the wiki just sends me in a loop of Chef's Knife/Tonberry Knife whenever I try looking for a proper item description, though I take it to mean both Chef Knife and Tonberry Knife are the same thing, and I wonder if Alex having the Chef's Knife, it can be used in the same way as Zack's Limit Break and summon a Tonberry? Perhaps the Tonberry's weapon form can be used in that way as a Limit Break? Here's a vid for context on what the DMW looks like.
View: https://www.youtube.com/watch?v=wytJb3qEcz4
Concerning Blue Magic abilities, there are four I know of that can be learned from the Tonberry, but one is from the
Mega Tonberry when it is Oversouled, a ruling from zagan would be needed to say if his Tonberry would count for learning that ability.
Traveler is a
Lore spell, FF6 Blue Magic, that damages an opponent based on the steps they have taken divided by 32 along with other factors to determine the damage dealt. You can see how powerful that can be against certain people, say a group of cape serial killers that travel the country, or just a group of
Travelers in general? This can be learned from a regular Tonberry so I hope you won't remove it from Alex's gains.
These next two are from FF XI,
Everyone's Grudge and
Light of Penance. As everyone is aware, Everyone's Grudge deals damage based on the number of kills made by the target, for a Blue Mage it's listed as a dark element spell and I imagine it still works the same way, and Light of Penance is a light element spell that reduces an enemy's TP, Tactical Points is how enemies and players use weapon skills/limit breaks in battle, along with casting
Blind and
Bind on the target.
The one from the Mega Tonberry is
Cry in the Night from FF X-2, an all-party non-elemental magic attack that costs 80 MP to cast and is considered the ultimate Blue Bullet spell for the Gun Mage, that games Blue Mage Job. As the wiki does a poor job explaining what that looks like, here's another vid.
View: https://youtu.be/dS18wiuPxgI?t=206
As there is no specific ruling on how far one can train a creature from this category, could the Tonberry be raised to become one of its variants like Master, King, or Mega and gain their items drops as well?