Summary
Have you ever heard of MacGuffins? Objects whose presence within the narrative makes the plot move forward. The heroes need the object to defeat the villain, or the villain needs it to accomplish their goal - bonus points if both the heroes and villains need the same object for their own reason.
This object can be many things, such as money, something of value, a place, or even a person. That said,Dungeons & Dragonshas multiple magical objects to offer your players during the adventure, such as rewards, treasure, or loot. Why not go one step further and make a magical object that actually moves the plot, then?

10Book Of Exalted Deeds And Book Of Vile Darkness
Two For One
The Book of Exalted Deeds grants multiple powers to its reader and is particularly useful for spellcasters. The Book of Vile Darkness also grants a bunch of powers, those leaning more towards evil.
You can have a villain seeking the evil book, and the party needs to use the good book against the bad guy. A search for two artifacts so you can pin one against the other is a fun concept for a campaign, and it won’t be the only pair we’ll suggest here.

9Cubic Gate
Multiverse Of Madness
If your story revolves around traveling along multiple planes, having an item that gives you such power is imperative. With the Cubic Gate, you’re able to choose five planes of existence to add to its sides (the sixth side is the Material Plane) and let players travel through them.
Unless they intend to make multiple trips without resting, the Cubic Gate will likely always have a charge to send them somewhere else, so it’s a safe object for this type of adventure.

8Eye And Hand Of Vecna
The Price Of Power
Another fun pair is having a villain going after thesetwo parts of Vecnato become more powerful. One of them is more than enough to upgrade your villain significantly, and both items on the same person even allow the user to cast Wish, so preventing that is very important.
You can also add the Sword of Kas into the mix, as it’s the only thing that can properly destroy these items and vice versa, meaning a player would have to use one of these profane items to stop the other for good, and that’s just an amazing narrative.

7Holy Avenger
For Fighting Fiends
Similar to how the Sun Blade has an important role in Curse of Strahd, you can use the Holy Avenger as a key item in a fight against fiends. If your story revolves around fighting multiple fiends or having an extremely powerful one as the BBEG, locating the Holy Avenger is a fun quest to have.
That said, it is a legendary weapon that can only be attuned by paladins. If that’s not something you want, you’re able to either change its attunement requirements (you’re the DM, after all) or use the Mace of Disruption, which is also effective against fiends.

6Mirror Of Life Trapping
Free Someone Or Prevent It
The Mirror is an item with a long description, but the gist of it is that it can trap a few people inside it. While it’s not impossible for someone to escape alone, not everyone is capable of it, so having a mission about freeing someone stuck on it - and learning how to free them - is a fun quest already.
Alternatively, an evil person could be trapped there, and the mission could be finding the Mirror before the villain frees whoever is in there. Trapping a villain who’s too powerful to be defeated by the group is also a fun assignment - you can use this one in many ways.

5Moonblade
A Living Weapon
Sentient weapons are already a fun type of item to have a narrative around them. The Moonblade is sentient and has many powers depending on how many wielders it has had; it can choose who wields it, and it can be either good or evil, depending on who created it.
You can use the same idea of it being the only weapon powerful enough to defeat the big bad, though the players will have to convince the weapon to help, or it can go in different routes, such as returning it to the creator’s family. But the sheer fact you have to prove yourself to the weapon opens a lot of narrative possibilities.

Alternatively, if you want another sentient weapon that is a bit darker, the Blackrazor is a good one.
4Sword Of Kas
A Living Weapon, But Worse
The Sword of Kasis an evil blade, powerful and bloodthirsty. It’s the perfect mix of being powerful enough to be worth its troubles, as the weapon will try to take over hosts who do not heed its demands.
It’s also effective against undead and has a hatred for Vecna, so if he’s the main villain of your story - or someone using his eye and hand - the sword might actually want to help, causing a more complex and interesting narrative.

3Talisman Of Pure Good And Talisman Of Ultimate Evil
Two For One, Part Two
These talismans can be used in a story similar to the books, but they’re both more battle-oriented. They have charges that can instantly kill an enemy, with the Tasliman of Pure Good being more effective against fiends and undead, while the Talisman of Ultimate Evil is more effective against celestials.
Just keep in mind that these items do not recover their charges, so both the party and the BBEG have to be careful when using them. You can use them for a BBEG fiend against an ally celestial or even have the party track down the evil one to fight a corrupted celestial - keeping in mind that anything that touches it that isn’t a fiend or undead will suffer damage but can still use it.

2Wand Of Orcus
Raise An Army
Probably the most dangerous item in the hands of a player - especially because failing to attune to it kills the character - the Wand of Orcus allows the user to summon undead with ease, making them powerful villains outright.
That said, the wand becomes even more dangerous if wielded byOrcus himself,so if you want to take this adventure to a high level, having a follower wield it until Orcus decides to step in and make everything worse can make a compelling story as the players get more powerful.

1Anything That Grants A Wish Spell
Do We Need To Explain?
Items like the Luck Blade, the Ring of Three Wishes, or an Efreeti Bottle with a guaranteed Wish spell would be more than enough for an item that compels everyone in the narrative. Whoever finds it first has a wish granted, no matter if it’s the party or the villain.
That alone is more than enough to fight for it, and you can even make a campaign with multiple parties chasing it for their own reasons, turning it into a race to find the item that grants a wish.