
Manicly good and a natural supplement/upgrade to Hallowed Mirror. Requires some build-around.
Getting the charges is a bit of work, but is'nt a terrible challenge for a focused combatant character (like characters usually are). Once the charges are ready the ability to negate very bad tokens makes the character better at literally everything! In one go you can resist a treachery and heal pain, prevent a missed attack and heal, safely pull up a clue and -heal-!
When the Empty Vessel is charged and you swap for Wish Eater it opens a big window of power where attacks get more accurate, tests and treacheries get easier to beat and your pain literally flies away. The benefits make the commitment worth it.
A little groundwork and item teck is required to make it easier to find the Empty Vessel early enough to get the charges, a friendly with a No Stone Unturned, a Tetsuo Mori. Generally the cards you need to make a Empty Vessel shine are good anyway.
Once the Empty Vessel is on the table and charged you need to carefully consider when to swap it. Some scenarios have enough enemies running around that you can get it transformed twice, other times you would save up 3 or 4 charges to do the one and only swap of the scenario. Do note that the swap trigger is Fast and not locked into your turn, so you can rest easy with 3+ charges until right when you need the help.
Finally: Akachi Onyele can use it and it, works, gooood for her. She really needs Relic Hunter to make it work but oh BOY, a combat specialized Akachi Onyele with Wish Eater can bulldoze through fights.