There's enough magic swords floating around out there I bet could run a game every day for a decade and still not run out of new ones to stock your hoards.
You know what I haven't seen too many of? Magic scabbards. Can't have a sword without a scabbard. It'd be inconvenient to carry, and vulnerable to rust. Here's twelve (D12) of them:
1. A History of Its Violence: Appears as an ornate, leather-bound book. Its cover is decorated with heraldry and images of clashing swords that change day-by-day. Its pages are normally blank, but a sword plunged into them will dissolve into ink and spread into words across them. These words will describe the entirety of its past and properties in exhaustive, boring detail that would take days to get through. Running your hand across the words lets you draw the sword again.
2. Deeper Goes The Crimson Ocean: A scabbard of rusted iron and polished mahogany. It is carved with flocks of bats in flight. The scabbard contains the blood of every victim of a sword it's held, which disappears into the scabbard the moment it's spilled, and is rendered weightless and uncoagulating. This is great for cleaning up crime scenes. If tipped out the blood flows from the scabbard's throat. It currently contains a large pond's worth of blood.
3. Scabbard of the Empty-Handed Warrior: Made of silver fir, adorned with delicate curlicues of actual silver. Anything can be placed in this scabbard, and drawn out as a sword of the same material. Most materials will probably make shitty swords, and break on a critical failure. If you don't put anything in, you can draw a sword of air that dissipates on any failure. As an example, if you put in a cockatrice's corpse, the sword will retain its petrifying power (until it breaks because it's made of meat, feathers, and bone). Other materials may have their own particular properties, even if they're subpar and break easily (e.g. obsidian, smoke, wight's finger, etc.).
4. The Serpent Sheathes: A trio of nigh-immortal snakes, sibilant siblings of uncertain origin. Each can swallow blades of a certain size, and if fed with living prey regurgitate those blades coated in their venom. If one could find a way to speak with them, they be a valuable, if serpentinely biased, source of history. They can't stand each other anymore and will refuse to be carried in the same party:
-Kipoka: White and purple. Delicate enough to wrap around one's wrist. Can swallow daggers, and nothing bigger. Her poison inflicts blindness on a failed save, and lasts for 1d12 strikes. She prefers animals no smaller than a squirrel.
-Dhaifuka: Red and yellow. Bears a spiny rattle on the tip of his tail. Can be worn as a belt. Swallows blades as big as longswords, and must be fed with a goat, or a pile of rabbits to regurgitate them. His poison halves a victim's strength on a failed save, and lasts for 1d8 strikes.
-Fuvuka: Black and green. Her tongue bulges obscenely. Must be draped around one's shoulders, if she is to be carried at all. Her poison causes death by throbbing of the brain on a failed save, and lasts for 1d4 strikes. She will accept nothing less than a horse to surrender the greatswords she swallows.
5. The Scamp's Stick: A gnarled wooden scabbard. While your sword's sheathed in it, it will appear as a simple walking stick, and you will appear as a feeble beggar, not even worth the effort of harassing. While it's in its walking stick form and used to support you, you can move at a normal pace even if you're exhausted and your legs are mangled.
6. Trucebringer: Made of olive-wood and burnished brass. It bears carvings of clasped hands. If Trucebringer holds a sword that has not yet been drawn, any others within 30 feet must contest its bearer in strength to be able to draw or nock their own weapon. If a treaty is sworn upon the scabbard, either party immediately becomes aware if the other breaks its terms.
7. Whispering Wind: A scabbard of clouded and rippling crystal. Swords drawn from it become invisible, and intangible to those they strike. Wounds dealt by such swords do not appear and take effect until after the swords have been returned to the scabbard. The appearance of wounds is accompanied by a rush of air towards its bearer's location.
8. Duelist's Delight: Made from bands of aspen and yew bound by rings of dark steel. Each round its bearer wields it in one hand they can decide whether it acts as a +1 shield, or a +1 club, with any penalties for dual-wielding with the latter being halved. Regardless of local custom, any blade drawn from it will be accepted as its wielder's weapon in a duel.
9. The Yearning Grasp: A scabbard of sticky willow-wood, decorated with gentle arcs of magnetite. If no weapon is within it, its bearer can attempt to draw a weapon within 30 feet into it. If that weapon is held by another they must save vs. wands to hold onto it, with a cumulative penalty of 2 each turn its bearer concentrates on the weapon. The scabbard adjusts its shape to fit the weapon.
10. The Spellsword's Sheathe: Adorned with purple-and-gold cloth. If its bearer succeeds in a save against a spell, there is a 2-in-6 chance that the sheathe will capture the spell. The next time a sword is drawn from it, it will cast that captured spell on the first target it strikes. The sheathe can contain only one spell at a time. While it contains a spell the gold sections of it emit a soft glow.
11. What Sound Prudence: A scabbard made of shark-leather, with a damascened locket and chape. When held, its bearer may consider fighting someone or something in their line of sight, and receive a notion of the difference in their power by the way the scales of its leather feel. If they're weaker than their intended opponent, the scales will feel proportionately rougher, and likewise smoother if they're stronger.
12. Scarseer: A grotesque construction of severed keloid tissue stapled together with gleaming bronze. Its locket is decorated with a bushel of fur resembling a lion's mane. Once a day, its bearer can access a vision of someone who's been wounded by a sword drawn from it, as Clairvoyance.