If an item is corrupted, characters are required to Elder Attune to the item, before they can use it, this takes no more than a few seconds. However, a character can only be Elder Attuned to a single item at a time and can only unattune from it by attuning to another Elder Corrupted item. This does not take up a regular attunement slot.

Optional: Elder Evil Corruption Transforming items by means of the powers of Elder Evils is naturally unpredictable, but can also create an item with new effects never before seen. Whether or not an Orb will corrupt an item can only be identified by casting a wish spell on the Orb. A regular identify spell only reveals the regular transformation.

This black and red, palm-sized orb feels cool to the touch. When it touches a non-artifact magic item while its command word is spoken, it transforms this item into a new item of the same rarity and type. The orb is consumed in the process.

So, you have this weirdly shaped and weirdly cold looking rock you got from some weird looking creatures made up of larvae, what does it do? Your natural inclination is to identify it, of course. I didn't want this to reveal the Elder Corruption, simply because I like some things to just be a mystery, and an item that precedes the existence of magic is a good opportunity for that.

This does imply though that this item is first of all very limited, which is at least how I would use it, and rather high level. Now the Star Spawn suit me, because the campaign I'm currently running is about that level, but still. I think there's definitely room to make the item available at lower level, however, I dread the idea of it becoming common. More on that later.

At first I wanted to design a couple of "void" beings that came from the dark places beyond, serving those things that precede magic and life as we know it. However, after rereading the Star Spawn entries in Mordenkainen's and their flavor text, I would probably just have some Star Spawn crash near the PCs, perhaps with edited stat blocks, and have them carry something like a single Harbinger Orb.

As opposed to some other documents I've chosen to actually put the background to this magic item in the back, instead of in the front, since I assume everyone reading only really cares about the item. Nevertheless, I'd like to point some things out about it.

So, the orb transforms a magic item in a new one of the same rarity and type, which means that an uncommon wondrous item becomes an uncommon wondrous item, a rare dagger, whatever the actual magic item is, becomes a rare dagger, etc. This dagger might have been a frostfang and after the orb it is simply a +2 dagger. As long as it is rare. When transforming an item, I would probably just use the tables in the DMG and keep rolling a d100 until I hit the right type. This does skew the minor/major magic items, since there is no real table where these are combined. An alternative, and perhaps the best way, is to use an online tool where you can actually classify the items on type and rarity and then roll an appropriately sized die.

When using the corruption, you can either roll on a specific table for that rarity with a d20, or simply roll a d100 and see what happens. This might create some insane items, like an uncommon weapon making your strength 19 or giving you disintegrate, but that's what you signed up for when you rolled that die.

Elder Corruption Now when it comes to the corruption, it says optional on the actual item, but I wouldn't treat it this way. To me, this item really is a one-in-a-campaign sort of item, not unlike the Deck of Many Things. Because of this, I always want every instance of this item to be memorable and special. Likewise I'm not entirely pleased with the corruption tables. When only using an item like this once, you want it to feel memorable. On one hand, for the sake of balance, you perhaps don't want only positive effects, because something with no downside to it is simply not interesting and just makes the items more powerful. On the other hand, when a 14th level party ruins one of their 12 rare magic items because they made it into a ring of x-ray vision that makes you blind, that's not really that big of a deal. Nor is it actually memorable. Some of this is down to players playing risk averse and this makes perhaps for a less "highlight-reel" sort of game, but to my mind it's a credit to good design when this play is also very fun and very memorable. That being said, I'm not quite sure what tables to use and if you choose to use this item it'll be up to you to figure out what suits your table best. Likewise, I'm not entirely sold on the Class features table, most of them should be pretty fun, but there's definitely room for you to change it up. Something about the actual mechanics though, I'd consider the effects that halve your hit points or change a random ability score to 10 to be permanent, however, this makes some of the effects, like make an ability score 19, exceptionally strong if you have several of these corrupted items. Since you would be able to Elder Attune to it once, and then sit on 19 Int forever, for example. You can choose what to do here, the safer play is to make it bound to the item, but I'd make sure of being sure before rolling on the tables. Likewise, to determine a random element you can roll a d6 (ignoring the 6), to choose an element in alphabetic order. The same goes for weapon types.