Trials introduces a new way to play completed worlds. Each world can be replayed in three levels of increasing difficulty, earning you Mastery Points along the way. Mastery Points can be assigned to Upgrades of your choice, permanently boosting all heroes.
Each difficulty increases the damage and health of the enemies, and adds a new negative perk.
First difficulty is called Vanguard, and it has one modifier: Corrupted. Corrupted perk causes your maximum health to drop every time an enemy does melee damage to you.
Second difficulty is called Elite, and it has two modifiers: Corrupted and Unstoppable. Unstoppable perk allows enemies that are above half health to move faster, and be immune to status effects (ie. stuns).
Third difficulty is called Champion, and it has three modifiers: Corrupted, Unstoppable and Infested. Infested perk causes enemies to sometimes spawn monsters on death.
Completing a trial for the first time gives you a Mastery Point. Head over to the Upgrades menu from the main page. From there you can choose which permanent upgrade you wish to improve. Then just click on the Empower button to use your Mastery Points.