The Upgradable equipment is a fan term referring to a category of very powerfull optionnal equipments in few games, even be the best equipment possible. Their distinctive feature is that they can be upgraded to be even more powerfull, each piece of equipment comes in 4 versions that become more powerful as they are upgraded.
Dragon Quest IX: Sentinels of the Starry Skies
The upgradable equipment make their first appareance in this game and are the best weapons and armours that can be found. The weapons can only be found in a Rang 10 Chest at 1% in the Treasure map Grottos when the armour can be dropped at 2% in different bosses of the Treasure map Grottos.
When found, they can be upgraded with the Krak Pot in the Quester's Rest inn multiple time. The first upgrade for any equipment require a Agate of Evolution and an Orb only dropped by the Legacy Bosses, the second upgrade require 3 Agate of Evolution and 3 Orb of the same colours. A third upgrade making the equipment even stronger is only accessible with a Alchemiracle when doing the second upgrade. If it doesn't succeed, a Reset stone can be combine with the equipment obtained to send it back to the first stage and start again.
Weapons
Axes (Purple Orb): 
Bad axe → Maxi axe → Climaxe / 
Galaxy axe
Boomerang (Silver Orb): 
Meteorang → Asterang → Stellarang / 
Galaxarang
Bow (Yellow Orb): 
Angel's bow → Archangel's bow → Aeon's bow / Seraph's bow
Claws (Red Orb): Dragonlord claws → Dragovian claws → Dragovian lord claws / 
Xenlon claws
Fan (Green Orb): Critical fan → Overcritical fan → Hypercritical fan / Dire critical fan
Hammer (Yellow Orb): Groundbreaker → Earthsplitter → Moonmasher / Starsmasher
Knive (Purple Orb): Deft dagger → Darting dagger → Dashing dagger / Dynamo dagger
Spear (Red Orb): 
Poker → Stud poker → Split-pot poker / Red-hot poker
Staff (Blue Orb): Knockout rod → Senseless stick → Catatonic cosh / Coma cudgel
Sword (Silver Orb): 
Stardust sword → Nebula sword → Supernova sword / 
Hypernova sword
Wand (Blue Orb): 
Bright staff → Shining staff → Brilliant staff / 
Aurora staff
Whip (Green Orb): 
Gringham whip → Mega gringham whip → Giga gringham whip / 
Über gringham whip
Armours
Shield (Green Orb) 
Brain drainer → Psyche swiper → Devilry drinker / 
Soul sucker
Armor 1 (Red Orb) 
Victorious armour → Glorious armour → Mythical armour / 
Legendary armour
Armor 2 (Blue Orb): 
Tropotoga → Stratotoga → Mesotoga / 
Exotoga
Armor 3 (Yellow Orb): 
Angel's robe → Archangel's robe → Aeon's robe / 
Seraph's robe
Headwear 1 (Purple Orb): 
Hallowed helm → Blessed helm → Wonder helm / 
Heavenly helm
Headwear 2 (Green Orb): 
Spring breeze hat → 
Summer cloud hat → 
Autumn shower hat → 
Winter sky hat
Handwear 1 (Red Orb): 
Vesta gauntlets → Diana gauntlets → Tempestes gauntlets / 
Sol Invictus gauntlets
Handwear 2 (Silver Orb): 
Apprentice's gloves → Master's gloves → Grandmaster's gloves / 
Godly gloves
Leg armour (Purple Orb): 
Invincible trousers → Immortal trousers → Eternity trousers / 
Infinity trousers
Footwear 1 (Yellow Orb): 
Hero's boots → Basilic boots → Emperor's boots / 
Boots of beatitude
Footwear 2 (Blue Orb): 
Sensible sandals → Sagacious sandals → Sapient sandals / 
Sentient sandals
Dragon Quest XI: Echoes of an Elusive Age
The Upgradable equipment make another appearance to this game with few changes. The weapons are the only equipment who can be upgraded and it's no more random elements to get the final version of the weapon, the armours are only found in their final version. Only the weapons who was existed in the previous game appear, the Greatsword and the Heavy wand doesn't have their own version.
The weapons weapons can be collected at various points in second act while three Forge manuals for upgrade them are found in act 3. The first is found in the Tower of Lost Time, the second in the Sage's Trial of the Drustan's labyrinth and the last is won with a wish from Drustan. The armours are dropped by monsters or forged by the Fun-size Forge.
Weapons
Sword (chest in Fortress of Fear or First Forest Whale way station): 
Stardust sword → 
Nebula sword → 
Supernova sword → 
Hypernova sword
Knive (65 Mini medals): 
Deft dagger → 
Darting dagger → 
Dashing dagger → 
Dynamo dagger
Boomerang (chest in The Manglegrove, Whale Way Station) 
Meteorang → 
Asterang → 
Stellarang → 
Galaxarang
Handy wand (Wheel of Harma third trial, 15 turns or less): 
Bright staff → 
Shining staff → 
Brilliant staff → 
Aurora staff
Whip (Octogonia casino, second act): 
Gringham whip → 
Mega gringham whip → 
Giga gringham whip → 
Über gringham whip
Spear (Chest in Fortress of Fear or First Forest Whale way station) 
Poker → 
Straight poker → 
Stud poker → 
Split-pot poker
Claws (Wheel of Harma third trial, 20 turns or less): 
Beastmaster claws → 
Dragonlord claws → 
Dragovian lord claws → 
Xenlon claws
Axe (Chest in the Battleground): 
Bad axe → 
Maxi axe → 
Climaxe → 
Galaxy axe
Armours
Brain drainer (Chest in The Battleground or dropped by Red mist)
Psyche swiper (Chest in Drustan's labyrinth or dropped by Knight abhorrents)
Devilry drinker (Puerto valor casino, third act or dropped by Hooper dupers)
Soul sucker (Ye Manifold Methods of Mighty Drustan forge manual)
Legendary armour (The Stuff of Legend forge manual or dropped by Labradrakes)
Exotoga (YeManifold Methods of Mighty Drustan forge manual)
Seraph's robe (Ye Manifold Methods of Mighty Drustan forge manual
Heavenly helm (The Stuff of Legend forge manual or dropped by Badonis)
Spring breeze hat (Styles for All Seasons forge manual)
Summer cloud hat (Styles for All Seasons forge manual)
Autumn shower hat (Styles for All Seasons forge manual)
Winter sky hat (Styles for All Seasons forge manual)
Trivia
- Some equipments, the Angel's robe and the Gringham whip, existed in previous games but Dragon Quest IX is the first game who make these equipment upgradable.
- The Red-hot poker exist only in Dragon Quest IX, be replacing by the Straight poker who become the second version in Dragon Quest XI while moving other weapons in the ligne, the Stud poker moves from second to third versions and the Split-pot poker move from the third place to final version.
- The first three versions of the weapons in Dragon Quest XI can't have any refinement, only the final version can.