They said this with WoD, too, despite the big option there being which Atomos you killed. Dude didn't even have a chest.Void Ark
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[2.0] The following items will now appear in the treasure chest of each party in an alliance when undertaking Syrcus Tower or the World of Darkness:
Wind-up Onion Knight / Puff of Darkness
That seems to be a gigantic easing in acquiring those two.