This Ancient Temple was designed to contain some ancient evil and two of its minions/lieutenants.
The earthquake that seems to have unleashed the undead horde appears to have broken the bindings that held this creature and one of its associates. One associate was still trapped and attempted to trick the party into letting it go and it succeeded.
The party assumes that one of the prior two creatures unleashed is the one dealt with by The Fallen Paladin.
There is a motif in the art of a great battle where a great evil was defeated and bound.
There is a door that the party could not touch without risking death, that some “chosen one” is meant to open. (Prophecy: Only the one who is worthy may enter. The one prophesied at the binding is the one who can renew the binding.)
The party, in the person of Zho Ni have the platemail of the ancient keepers of the temple and the magical holy symbols of its two orders of Virtue (platinum) and Truth (gold). These symbols adorn the tabards of the undead in the temple and one wearing one of these symbols is able to direct these undead or is ignored by them.