You now have access to the Phantasmal Arena, a place where you can challenge the echo of beings from across the multiverse in a contest of might or skill. When you manage to defeat an opponent all of their strength and abilities would then become your own.
You can enter the arena at will whenever you want. No matter how long a challenge takes, only 1 hour will pass in the real world at maximum. The arena will automatically generate an echo for you to challenge when you have achieved victory against your opponent or a week in the outside world has passed. The Echo is randomly generated but generally, the opponent will be stronger than what you are currently (at least 20% stronger and at most 50%), you will always have a non-zero chance of defeating the echo generated for you.
When you enter the arena you will be returned to your current prime self. Any injury or death suffered when challenging an echo will be completely reset after the attempt is over but mental fatigue and any trauma that you gain in a match will not be healed, you have 10 attempts at challenging the echo per day. The healing effect does not apply to injuries that occur outside of the arena so when you exit the wound you have acquired beforehand will return to you.