Greetings friends of Greyhawk! Today I'm going to try something out. After recently musing about one-sided battles with Istus and Ulaa, I started thinking about the unique magic items belonging to the gods of Oerth. Well, for the most part they are actually relics and artifacts of which no mortal could hope to copy. Time and again though, some of these magic items fall into the hands of PCs either by accident or by design. One such artifact is the Kanteel of the Oldest, the musical instrument of the "Laughing Rogue" Olidammara, god of wine, rogues and revelry. A kanteel (actually spelled kantele) is a Finnish/Karelian stringed instrument. The information below is my attempt at a 5E conversion. Enjoy!
Kanteel of the Oldest
Wondrous item, artifact (requires attunement by a bard)
The Kanteel of the Oldest is an exemplary example of its kind, vastly superior to even an instrument of the bards in every way. A creature that attempts to play the Kanteel without being attuned to it must succeed on a DC 20 Wisdom saving throw of take 4d4 psychic damage.
Spells. You can use an action to play the Kanteel and cast one of the following spells (save DC 18) from it: calm emotions, charm person (as 3rd level version), charm monster* (as 6th level version), creation (as 6th level version), dispel magic, fog cloud, legend lore or programmed illusion. Once the Kanteel has been used to cast a spell, you can't cast that spell again from it until the next dawn.
Easy Come. Olidammara occasionally lends this artifact to mortals or allows it to be stolen for a time. While the Kanteel is on your person, any spell slot you expend to cast a bard spell counts as a spell slot of one level higher.
Easy Go. Ownership of the Kanteel is always temporary. Olidammara can call the Kanteel of the Oldest to his person at any time, even across planar barriers. When the Kanteel vanishes, you receive a permanent Blessing from Olidammara (see DMG page 227).
Destroying the Kanteel. While this instrument looks fragile and ancient, it is impervious to all damage and magic, short of that caused by another artifact. Usually Olidammara will summon his Kanteel back to his hand should anyone manage to scratch it. Bardic lore says the Kanteel's strings will break permanently if it is played in front of an audience of three or more unappreciative demon-lords or arch-devils.
*see Xanathar's Guide to Everything
Sean K. Reynolds, Core Beliefs: Olidammara, Dragon #342
Gary Gygax, Deities & Demigods of the World of Greyhawk, Dragon #70
Gary Gygax, World of Greyhawk Setting