Okay!

So here is what happened.

During the event, some players were getting multiple items from a boss defeat, when only one should have been dropped. This turned out to be more widespread than we originally thought. This is clearly an unfair advantage. We have fixed it going forward for future events.

At the end of the event, we ran a script to remove the extra items. We've taken measures to verify that the items removed were extraneous. Everyone now has one item for each time they killed Ixtab/participated enough.

Contrary to popular belief, this didn't remove items you farmed after completing goals.

As requested, here is a list of all the items affected: