Two VIP keys. It would be of value worth more than the Keys spent and with a higher chance to gain Mythics than the keys they spent, after all. (For absolute clarity, this is a joke, this should never happen again.)
(Also to their credit they did eventually make it right after an immense amount of backlash even through the “matter was considered closed” by mailing out the 2 VIP keys PLUS a new troop of the same rarity for each incorrect pull).
So what should actually happen? I’m not even sure what can be considered “fair” here because anyone pulling for AW did rightfully have a 50/50 chance at Yvendra once pulling a mythic if everything worked as implied by every single statement on their help site. Even the people that pulled 4 Yvendra could have still realistically done so with the expected loot tables. A one time only “trade” of a Yvendra pulled with event keys into AW would be nice, but is likely to be seen as significantly more “generous” than is likely. Precedent for “making this right” (if this isn’t one of the 50/50 times where the issue is completely just ignored or bulldozed over) would be a random mythic between the two that were expected to be available… but for anyone seeing this and already angry, would they really be satisfied by trading in their Yvendra for a “random” new mythic in the event key pool only to receive Yvendra again sight unseen as your “random” reward? Be honest, how many of you at this point would trust that?
This is probably going to have a messy outcome no matter what with a lot of people feeling pissed off or cheated. If you expect any kind of resolution at all, though, you have to press the issue and get people talking about it. Do NOT, I repeat do NOT abuse the support staff, but don’t just roll over on this - it is important, they did not properly communicate a major omission in chest drops and it should be seen as this, regardless if they intended to have chest drops be this or not. People were asking if Yvendra would even be in chests last week and this didn’t even get answered. This was a failure on their end and you should not just suck it up.
I can hope for the best possible outcome of simply allowing a 1:1 trade for the expected mythic, but the thing I really want to happen out of all of this is for what is actually in chests right now to be completely and accurately communicated at all times. From outright drop errors to “misunderstandings”, this stuff has happened way too often for this game when it is their bread and butter and only about half of them have what I would consider a favorable resolution.
So I’ll say again the same thing I say every time - this is hopefully the last time this happens.