Upgrade items are items you can find via different methods that can be only obtained a limited number of times and permanently affect your character without taking space on the inventory. They can be seen in the codex.
Yeah, I think I've suggested this before (except someone else posted it) I may be taking some ideas but I have some of my own.
- Quiver (Uncommon, Rare, Epic): Special slot that holds a bunch of arrows. Crafted on the bench, each one uses more resources than the last. You can craft up to 3 for a 300 arrow capacity.
- Storm Power Bank (Epic): Gives you an extra power cell that automatically powers any vehicle you're driving. Recharge by eliminating storm-wild enemies, consuming storm fruit (or Nectar) or spending time in any storm. Gives unlimited energy while on the storm. Crafted with greater storm cores and (full) power cells.
- Dark gizmo (Shared, Epic): Mysterious gizmo that serves no use in this state. Allows you to craft Storm Power Bank and gives you the recipe.
- Storm Compass (technically already exists, shared, rare): Reveals the location of off-map storms. Obtained via the Storm Chasers camp.
- Raven Reacher (shared, epic): Reveals the location of Raven.
- Survival Compass (Rare): Reveals nearby enemies and enables a minimap. Crafted using some early-middle game materials.
- Treasure Tracker (Epic): Reveals nearby chests (both unlooted containers and supply chests).
- Bus card (Shared, Common): Lets you use and build Battle Bus stops. Obtained by talking to Tricera Ops.
- Bus membership (Shared, Rare): Reduces the cooldown time from 15 seconds to 5 seconds, and reduces skydive limit (allowing you to reach the ground faster). Talking to Tricera Ops will start a journal quest to thank the bus driver 20 times. Once finished, can be crafted using a rift shard and other stuff.
- Klombo Runes, Storm Runes and Klombo Props: Shows how many have you collected (and the total number available) for each.