Sculk Gleam is the glowing block that lights up the caves of the Otherside, the dimension from the Deeper and Darker mod, and it hangs in clumps from the roof much like Glowstone does in the Nether. Mixed in with it you’ll find 
Porous Sculk Gleam, which slowly fills with 
Gleam Gel that you’re able to shear off and use.
This page covers those blocks along with the other light sources the mod adds, like the 
Gloomslate Light and the 
Block of Lite. Most of them were added in version 1.4, so the 1.20.1 version of the mod, which stops at 1.3.3, only has the plain Sculk Gleam.
Obtaining
Sculk Gleam generates in large clumps hanging from the ceiling of the Deeplands and the Echoing Forest, where it’s a lot more common, and the Echo Trees there often have a block of it stuck under their leaves. It drops itself when broken, without needing Silk Touch, and a hoe is the quickest tool for it.
Roughly one block in every seven of each clump is Porous Sculk Gleam instead, and you’ll notice it glows a little dimmer than the plain Sculk Gleam around it. It drops itself too, so you’re able to take a few home and set up a Gleam Gel farm wherever you like.
The Gloomslate Light and the 
Gleam Gel Block are both crafted, from Sculk Gleam and Gleam Gel. 
Lite is different though, as its only source in 1.4.1 is breaking Enriched Gloomslate Bricks, which don’t generate anywhere in Survival yet, so Lite and its blocks are Creative only for now.
Porous Sculk Gleam
A Porous Sculk Gleam block slowly fills up with gel over time, in six stages, and it glows a little brighter with each one. Once it’s full, using Shears on it gives you two Gleam Gel and empties it back to the start, without breaking the block.
It fills on random ticks, a bit like a crop grows, so it’ll only keep going while it’s in a loaded chunk near you. A Comparator reads how full it is, giving a signal from 0 to 6, which makes it easy to build something that tells you when a whole wall of them is ready to shear.
Uses
Sculk Gleam gives off the brightest light there is, the same as Glowstone or a Sea Lantern, so it’s the best block to light up an Otherside base with. Four 
Gloomslate around one Sculk Gleam make a Gloomslate Light, which gives the same light in a more polished brown frame.
Gleam Gel is used for brewing, as adding it to an Awkward Potion gives you a Potion of Glowing, which makes you glow and stand out through walls for three minutes. It’s also the food Sculk Snappers like, so it’s worth keeping some around if you’re raising any of your own.
Nine Gleam Gel make a Gleam Gel Block, which is a soft, sticky block you’ll sink into and move slowly through, a bit like Cobweb. Landing on it doesn’t hurt at all, and it sticks to blocks next to it when pushed by a Piston, like Slime and Honey do, though it won’t stick to either of those.
The Block of Lite is made from four Lite and gives a full light level, the same as a Froglight, and you can turn it back into four Lite whenever you like. Surrounding it with Gloomslate makes a 
Bordered Block of Lite, though you’ll need Creative to try either of them out at the moment.
FAQ
Find a Porous Sculk Gleam in the clumps of Sculk Gleam on the Otherside’s ceiling and wait for it to fill up with gel. Once it’s full, using Shears on it gives you two Gleam Gel and empties it, so you can keep collecting from the same block.
You don’t, as Sculk Gleam and Porous Sculk Gleam both drop themselves when you break them with any tool. A hoe is the fastest way to mine them, and the porous kind keeps working once you’ve placed it back down at home.
Lite crafts into a Block of Lite and a Bordered Block of Lite, both of which give off a full light level. It can’t be found in Survival in version 1.4.1 though, since its only source is Enriched Gloomslate Bricks, which only appear in the Creative menu for now.
