The 
Orb of Prophecy is an item from the Eternal Starlight mod that opens the Starlight Portal, and it’s the one thing you’ll need before you’re able to reach the Starlight Dimension. You’ll get your first one from the Gatekeeper at a Portal Ruin in the Overworld, and it can be used on the portal frame as many times as you like without being used up.
Once you’re inside the dimension, more of them can be crafted from 
Glass and 
Blue Starlight Crystal Shards, which is handy for opening a second portal somewhere else. In older versions of the mod the orb also cast spells and tracked bosses, but that was taken out along with the mana system, so now it only opens portals.
Obtaining
There are three ways to get an Orb of Prophecy, and the first time round you’ll need to go through the Gatekeeper, as the crafting recipe uses shards that only exist inside the Starlight Dimension. After that, you’re able to either buy more from him or craft them yourself, whichever is easier at the time.
From the Gatekeeper
Every Portal Ruin has a Gatekeeper sitting in front of its frame, and challenging him to a fight is the usual way to get your first orb. When his health runs out he’ll give up rather than die, and the rewards that appear in a 
Loot Chest will include an Orb of Prophecy and a 
Glimmering Tablet the first time you beat him.
If you’ve already killed the Ender Dragon, you won’t have to fight him at all, as talking to him will drop a 
Loot Bag with the same rewards inside. The fight itself is covered on The Gatekeeper page, as he’s got quite a few different attacks.
Trading for More
After beating him, or the Ender Dragon, the Gatekeeper will sell you an Orb of Prophecy for a single 
Starlight Silver Coin. He trades coins for 2 
Iron Ingots or 1 
Emerald each, so a spare orb only really costs a couple of Iron Ingots, and this trade can be used 20 times before it runs out.
Crafting
The recipe needs 4 Glass and 5 Blue Starlight Crystal Shards, with the shards in a plus shape and the Glass filling in the corners. It’s cheap to make once you know where the shards are, though you’ll need to be in the Starlight Dimension first to find them.
The shards come from 
Blue Starlight Crystal Clusters, which grow on the huge crystal formations in the Crystallized Desert. Breaking one with a Pickaxe gives 4 shards, and Fortune will add more on top, whereas breaking it with anything else only gives 2.
The Crystallized Moth is another source, as each one drops 1 to 2 Blue Starlight Crystal Shards and the same amount of 
Red Starlight Crystal Shards when it’s killed. These live in the caves under the Crystallized Desert and won’t attack unless you hit them first, so it’s usually easier to mine the clusters instead.
Usage
The Orb of Prophecy has one job, which is opening the Starlight Portal. Hold it and use it on a frame of 
Chiseled Voidstone, and as long as the frame is a complete diamond with nothing inside, the portal will fill in and you’ll be able to walk through.
Opening a Portal
The frame found in every Portal Ruin is the smallest size, made from 8 Chiseled Voidstone, and it’ll work straight away once any Vines or leaves inside it have been cleared. Using the orb on a frame that isn’t finished, or one with a block in the way, won’t do anything, so it’s worth checking the whole diamond before trying again.
You’re able to build your own frame anywhere, including right next to your base, and the orb will open it the same way. Bigger diamonds work too, and the orb works out the size by itself, so there’s no need for a different item for larger portals.
It Isn’t Used Up
The orb stays in your hand after opening a portal, which means one Orb of Prophecy is enough for every portal you’ll ever build. It’s still worth crafting a spare once you’re in the dimension, though, since losing your only one outside of a portal would mean going back to the Gatekeeper.
Tips
Remember, the Gatekeeper only hands out the orb the first time you beat him, so if you lose it, the trade with a single Starlight Silver Coin is the quickest way to replace it. It’s worth grabbing some extra Chiseled Voidstone from him while you’re there as well, as 8 cost just one coin.
It’s worth mining more clusters than the orb needs, as Blue Starlight Crystal Shards are also used for the 
Crystal Crossbow, the 
Crystal Greatsword and the 
Blue Starlight Crystal Lantern. Both weapons need Golem Steel as well, which comes from the Starlight Golem, so they’re something to come back for later on.
FAQ
It opens the Starlight Portal, which is a diamond-shaped frame of Chiseled Voidstone that takes you to the Starlight Dimension. The orb used to cast spells in older versions too, but that was removed along with the mana system, so these days opening portals is all it’s used for.
Your first one comes from the Gatekeeper at a Portal Ruin in the Overworld, either by beating him in a fight or by talking to him after you’ve killed the Ender Dragon. After that, he’ll sell more for a Starlight Silver Coin each, or you’re able to craft them from Glass and Blue Starlight Crystal Shards.
Hold it and use it on any of the Chiseled Voidstone in a Starlight Portal frame, and the portal will open as long as the diamond is complete and empty. If nothing happens, check for Vines or leaves inside the frame, as those are the usual reason it won’t light.
It isn’t, as the orb stays in your hand after the portal opens, so one of them is enough to light every portal you build. It’s still worth keeping a spare in a chest though, just in case you lose it somewhere in the Starlight Dimension.
