Arena Key art
The Arena Key is a currency, which is required to enter The Arena. One must be expended with each entry. It can be picked up as loot from node rewards in the Monolith of Fate, or in The Arena between waves.
The Arena Key of Memory is a rare variant that starts the Arena from an advanced position. It can be obtained as a node reward in empowered timelines. When used, the wave counter will be half of the wave reached in the last Arena run, rounded to the nearest 10, but at least 100.