Rarity
Rarity is a property that applies to all items, loosely indicating their value and the difficulty through which they are obtained. An item's rarity is indicated in-game by the color of its name text. An item's rarity can be raised or lowered by up to two tier depending on its modifier.
Tiers
is in tier -2. Any item with a curse is indicated by this rarity with a purplish-reddish name color. Items with the Cursed rarity cannot be upgraded or downgraded in their tier despite still being able to acquire modifiers like any other item.
is in tier 12. Items of the Butterscotch rarity are usually obtained after defeating Quantux and through I.C.A.R.U.S., such as the Flakjack or Quantum Injector.
is in tier 13. Items of the Crimson rarity are obtained towards the end-game of Terraria Origins. These items are either crafted from the Elderforge or Interstellar Sampler, and include items like Black Hole Bombs and Eyndum Armor.
is in tier 14. This tier consists of Butterscotch and Crimson items that have high-level modifiers. No items have this as a base rarity.