Even though Horizon Forbidden West follows an open-world formula, the game is dotted with various roadblocks players can’t overcome without special items. One of those Metroidvania-esque obstacles are growths of red, crystalline fungi called Firegleam that plays won’t be able to clear until they’ve progressed through the main story.
Odds are you will first discover these red crystals sticking to various walls and doors throughout The Daunt and No Man’s Land. When scanned, they are classified as “Anomalous Growth,” and their description reads: “Hybridized crystalline and fungal growth of unknown origin. Invulnerable to impact. Special gear required to clear.” That last sentence should be your first clue. Much like how the Pullcaster lets Aloy grapple certain items and ledges, a similar device lets her destroy the red crystals. Fortunately, you don’t need to look far for this piece of “special gear.”
During the main quest “Death’s Door,” you will enter a facility (or at least you’ll try to). The door doesn’t open all the way, and the only way to unstick it is by using some Firegleam that coincidentally grows on it. The side character Sylens then hands over blueprints for an item called an Igniter, which can detonate the red crystal and help you progress through the mission. In order to create this gadget, you’ll need the oil from a Kindle Weed Plant and a Spark Coil.
The Kindle Weed is easy to find since the game marks its location on your HUD and map. Just follow the beacon to a nearby lake, and you should get the item. Although, if you explore enough, you might have the oil before the mission. The Spark Coil, however, is a tad more complicated since you need to extract one from Leaplasher’s power cell. Not only do you need to find a Leaplasher (you should find a pack of them near the lake with the Kindle Weed), you also need to remove the power cell before you destroy the robot.
In Horizon Forbidden West logic, this means you should scan the robot with Aloy’s focus, scroll through its parts until you find the power core, and then target the canisters at the base of the Leaplasher’s tail. One solid hit and the item will fly off, ready for retrieval. Of course, you will probably need to fight the Leaplashers afterward, but once they’re defeated, you can collect the parts and move on to the final task.
As with the Pullcaster, you can build the Igniter by visiting a workbench. You should find one just outside the facility. Interact with the workbench, scroll down to the Special Gear tab, and craft the Igniter. To use it, walk up to any patch of red crystals and interact with them via the R2 button. Oh, and be sure to step back a safe distance to watch the fireworks; you don’t want to get caught in the blast.
Now that you know how to craft an Igniter, you can clear out any batch of Firegleam you come across.