Diablo 4 Item Upgrades
Item upgrade item (yogaasanas.science) upgrades allow players to increase the item level of items that can be equipped, such as weapons or armor, as well trinkets above a certain threshold. They can be done at any upgrader NPC with the appropriate currency.
Slots are used to add upgrades to equipment in order to gain attributes bonuses and other effects. They are generally slot-restricted, however, there are certain universal upgrades.
Rerolling
A player can roll an upgrade to an item upgrader in Diablo 4. This is done through the Level Up mechanic, which pauses the game and displays a list of four randomly selected upgrades. The player is able to select one of the upgrades and continue the battle. Rerolling is the same price as the normal Level Up. Players should be cautious to select the correct upgrade, since they won't know the new stats until the item upgrader mod has been changed.
The rarity of an item level upgrade and its the level of its upgrade determine it.