The other week on the Skyrim subreddit, a player explained that, despite years of playing Bethesda's vehicle for cool mods, they'd come across something they'd never seen before: craftable spiders you can throw at people. Spiders that explode into flame, jumping shock spiders, poison spiders, mind control spiders, and more. Over the next several days, players either admitted they hadn't noticed them either, or crankily declared that everybody knows about the Skyrim mind control spider grenades, come on.
One reason the spiders flew under the radar for many players is that they're part of the Dragonborn DLC, and can only be found on the island of Solstheim. If you want to see them for yourself, you'll need to go to Windhelm's dock and find a ship that will sail to the port of Raven Rock for 250 gold, then get stuck at the introductory cutscene thanks to one of your mods and just use Skyrim's console commands to teleport yourself there.
A dungeon called White Ridge Barrow on the island's north is where you're headed (the location code is DLC2WhiteRidgeBarrowExterior01 if you're using the coc command). Inside are some reavers (dead), and spiders (angry). Make sure to grab albino spider pods from those you kill, or the eggs lying around.
Inside a locked cage in the White Ridge Sanctum area you'll find a dead dark elf and an imbuing chamber, along with a journal and a book of recipes. Those contain guidelines for using the imbuing chamber to combine spider pods with gems and other ingredients, thus creating spider scrolls. The UESP has a handy list of spider scroll recipes if you're not up for experimenting. Note the spider pods in this dungeon don't respawn, though there is a single spot near Bloodskal Barrow where they do.
Once you've crafted some spider scrolls, you can equip one in each hand and throw them to use. Those made with damaged albino spider pods will explode when enemies are within range, while undamaged pods result in pet spiders that follow you around until destroyed. The mind control variety latch onto targets and make them your allies for 30 seconds, which can be super useful if you're trying to complete the Dark Brotherhood questline without technically killing anybody, as YouTuber ymfah did.