The Collector

The Collector is an NPC in Dead Cells. He invites the player to give him cells and blueprints, in return for experimental items and more power. All purchases from the Collector are carried over through each run.

Upgrades
There are four types of upgrades: General improvements, weapons, and skills; the latter two of which will unlock or improve a specific item, after giving the Collector that item's blueprint.

The Healing Potion I is required for every other upgrade, but weapon and skill upgrades have no other requirements besides blueprints.