To the creator(s):
Very nice! Thanks for making this lovely showcase for the hidden material from the game we all love!
I'm the author of the Data/Mechanics Guide and debugger topics here on GameFAQs, so here are some thoughts from my areas of expertise, in the hope that they can be of help. I will try to avoid anything overly technical, since that doesn't seem to be the focus here.
You are, of course, welcome to use this information on the site; just please give credit where appropriate.
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Items:
First, be aware that DEFense is not a single quantity. There are 8 Elemental DEFenses: Slash, Pierce, Blunt, Heat, Cold, Electric, Force, and Status FX. For more information, see my Data/Mechanics Guide:
http://www.gamefaqs.com/ps/198537-saga-frontier/faqs/58412
Jump to [EFPRO-2] and scroll down to the section beginning with "EDV = Effective DEFense Value."
JerryArmor: Equipped by the Enemies Unknown and Gelatin, this Torso Armor gives +102 Blunt DEF, +38 Slash and Pierce DEF, and +6 DEF to all other Elements. It also grants Immunity to the following Ailments: Angry, Blind, Charm, Faint, Knockback, Mess, Palsy, Sleep, Stun, and Venom.
SlimyArmor: This Torso Armor gives +32 Blunt DEF, +16 Pierce DEF, and +8 DEF to all other Elements. It is Equipped by many Enemies, primarily to boost their overall Blunt DEF.
SkeleMail: This Torso Armor is Equipped by most Undead Enemies (and several of the later ones Equip multiple copies). It gives +32 Pierce DEF, +16 Slash, Cold, and Electric DEF, and +4 DEF to all other Elements. It also grants Immunity to the following Ailments: Angry, Blind, Charm, Faint, LP Damage, Mess, Palsy, Sleep, and Venom.
WhiteDress: This Suit does give +40 DEF against all Elements, but does not grant Immunity to Blind; rather it grants Immunity to the following Ailments: Angry, Charm, Faint, Mess, Palsy, and Sleep.
I am not aware of any way in which it is actually used in the game. Notably, it is not used when Emelia changes into her wedding dress sprite to fight Diva, as has occasionally been speculated.
FovosGrail: This Accessory is Equipped by the KylinJr PC Monster Form and by the following Enemies: MaskCat, Straysheep, Suzaku, SuzakuJr, Cyclops, Chariot, Giant, Jotnar, Gargoyle, Lamia, Siren, Wormbrood, and by the special UnicornJr and Tidi that accompany MasterRing.
It gives +25 Status FX DEF, +1 DEF to all other Elements, and Immunity to the following Ailments: Angry, Charm, Faint, Mess, Palsy, and Sleep.
V-Special: This Item is secretly Equipped when V-MAX is used and until V-END. It is this Item (and only this Item) which allows the use of StarlightShower and CosmicRave, so it is not functionally identical to V-System. V-System, by contrast, is what allows the use of V-MAX, which in turn Equips V-Special. Yes, you can shortcut the process and prevent V-END by just hacking V-Special on instead of V-System, but be aware that this will also prevent the normal effect of V-MAX, which boosts each Stat from STR--CHA by 50% of its Base Value.
Also note that, while Equipped, V-Special itself boosts Max HP by +100 and STR--CHA by +15, which is in addition to the effect of V-MAX.
DragonCannon: Despite the name, this is not a Weapon at all. Rather, it is an Item Equipped by Thundragon, RedDragon, and BlackDragon Enemies, primarily in order to grant Immunity to the following Ailments: Angry, Blind, Charm, Faint, Mess, Stone, LP Damage, Palsy, Stun, and Venom.
LastRing: This Item is Equipped by many Boss Enemies and simply grants blanket Immunity to all Ailments.