One Ring Shop to Rule Them All

Run by an elderly Goliath by the name of Thavalock and his wife Brumhilda Hogswallop (half-elf, also elderly but stoutly built). The couple are incredibly cheerful and welcoming, they aid any they can, but do not haggle on any goods ever, for all of their prices are set fairly for the wonderous items they keep.

Inventory

 * Armor of Invulnerability - 500,000gp
 * You have resistance to nonmagical damage while you wear this armor. Additionally, you can use an action to make yourself immune to nonmagical damage for 10 minutes or until you are no longer wearing the armor. Once this special action is used, it can't be used again until the next dawn,

Plate consists of shaped, interlocking metal plates to cover the entire body. A suit of plate includes gauntlets, heavy leather boots, a visored helmet, and thick layers of padding underneath the armor. Buckles and straps distribute the weight over the body.
 * Belt of Storm Giant Strength - 200,000gp
 * While wearing this belt, your Strength score changes to a score granted by the belt. The item has no effect on you if your Strength without the belt is equal to or greater than the belt’s score. STR 29
 * Luck Blade - 500,000gp
 * You gain a +1 bonus to attack and damage rolls made with this magic weapon. While the sword is on your person, you also gain a +1 bonus to saving throws.

Luck. If the sword is on your person, you can call on its luck (no action required) to reroll one attack roll, ability check, or saving throw you dislike. You must use the second roll. This property can't be used again until the next dawn.

Wish. The sword has 2 charges. While holding it, you can use an action to expend 1 charge and cast the wish spell from it.
 * Cubic Gate - 300,000gp
 * This cube is 3 inches across and radiates palpable magical energy. The six sides of the cube are each keyed to a different plane of existence, one of which is the Material Plane. The other sides are linked to planes determined by the GM (Abyss, Mechanus, Celestia, Feywild, Shadowmoor).

You can use an action to press one side of the cube to cast the gate spell with it, opening a portal to the plane keyed to that side. Alternatively, if you use an action to press one side twice, you can cast the plane shift spell (save DC 17) with the cube and transport the targets to the plane keyed to that side. The cube has 3 charges. Each use of the cube expends 1 charge. The cube regains 1d3 expended charges daily at dawn.
 * Deck of Many Things - 500gp
 * Efreeti Chain - 150,000gp
 * (Chain Mail) While wearing this armor, you gain a +3 bonus to AC, you are immune to fire damage, and you can understand and speak Primordial. In addition, you can stand on and walk across molten rock as if it were solid ground.

Made of interlocking metal rings, chain mail includes a layer of quilted fabric worn underneath the mail to prevent chafing and to cushion the impact of blows. The suit includes gauntlets.
 * Iron Flask - 200,000gp
 * This iron bottle has a brass stopper. You can use an action to speak the flask's command word, targeting a creature that you can see within 60 feet of you. If the target is native to a plane of existence other than the one you're on, the target must succeed on a DC 17 Wisdom saving throw or be trapped in the flask. If the target has been trapped by the flask before, it has advantage on the saving throw. Once trapped, a creature remains in the flask until released. The flask can hold only one creature at a time. A creature trapped in the flask doesn't need to breathe, eat, or drink and doesn't age.

You can use an action to remove the flask's stopper and release the creature the flask contains. The creature is friendly to you and your companions for 1 hour and obeys your commands for that duration. If you give no commands or give it a command that is likely to result in its death, it defends itself but otherwise takes no actions. At the end of the duration, the creature acts in accordance with its normal disposition and alignment.
 * Ollamh Harp - 150,000gp
 * An instrument of the bards is an exquisite example of its kind, superior to an ordinary instrument in every way. Seven types of these instruments exist, each named after a legendary bard college. A creature that attempts to play the instrument without being attuned to it must succeed on a DC 15 Wisdom saving throw or take 2d4 psychic damage.

You can use an action to play the instrument and cast one of its spells: Fly, Invisibility, Levitate, Protection from Evil and Good, Confusion, Control Weather, Fire Storm. Once the instrument has been used to cast a spell, it can’t be used to cast that spell again until the next dawn. The spells use your spellcasting ability and spell save DC. When you use the instrument to cast a spell that causes targets to become charmed on a failed save, the targets have disadvantage on the saving throw. This effect applies whether you are using the instrument as the source of the spell or as a spellcasting focus.
 * Ring of Spell Turning - 150,000gp
 * While wearing this ring, you have advantage on saving throws against any spell that targets only you (not in an area of effect). In addition, if you roll a 20 for the save and the spell is 7th level or lower, the spell has no effect on you and instead targets the caster, using the slot level, spell save DC, attack bonus, and spellcasting ability of the caster.
 * Robe of the Archmagi (Good) - 400,000gp
 * This elegant garment is made from exquisite cloth of white, gray, or black and adorned with silvery runes. The robe's color corresponds to the alignment for which the item was created. A white robe was made for good, gray for neutral, and black for evil. You can't attune to a robe of the archmagi that doesn't correspond to your alignment. You gain these benefits while wearing the robe: If you aren't wearing armor, your base Armor Class is 15 + your Dexterity modifier, you have advantage on saving throws against spells and other magical effects, your spell save DC and spell attack bonus each increase by 2.