For each weapon you can unlock one of the two alternative modes. Then for each mode there are two upgrades, which unlock the third upgrade.
Then you can also upgrade your health, armor and ammo capacity. And pairing some upgrades gives you additional upgrades, like longer ammo pull.
Then there are runes. Which mostly enhance stuff like your finishers.
Then there are armor upgrades. That don’t upgrade your armor, but can, for example, reveal all items on the map.
Then there are fortress keys, called sentient batteries. Those unlock access to armor and weapon upgrades in the hub.
Then there are Purple Keys. Collecting a key and finding a door on a level throws you into a challenge arena. And if you complete 6 of those, you get the superweapon, Unmaykr.
You see where this is all going?
