So, a lot of people have figured out that you can use this to evade the Harbinger multiple times in one turn without having to re-engage it (especially good with someone like Rita Young who would be better at evading it than fighting it). Well, I have an even more janky proposition for you:
Suppose that you're engaged with enemies and you have Entombed in your threat area. You provoke an AoO (or get damaged through some other means), it would defeat you except that you have Cheat Death in your hand, so you play that. Normally, the first step of Cheat Death is that you disengage from each enemy engaged with you, but Entombed prevents this from happening so you go to the next step, discard all cards in your threat area. This includes both Entombed itself, and the enemies that you are engaged with.
But wait, it gets better...
Because Cheat Death is not expecting to discard enemies at all it has no text preventing it from discarding Elite enemies. This means that if you have the Harbinger of Valusia engaged with you, you simply discard her from play; Achievement unlocked.
But it gets even better...
Normally, in the resolution to The Doom of Eztli, if you haven't defeated the Harbinger, you would record that she is still alive, which means that she comes back in future scenarios, however the actual text of the resolution is as follows:
If the Harbinger of Valusia is still in play or set aside, record in your Campaign Log that the Harbinger is still alive. Next to this, in parentheses, record how much damage is on the Harbinger of Valusia.
In general, if the Harbinger is not in play or set aside, she is in the Victory Display, but if you somehow discard the Harbinger, she will be out of play and not in the Victory Display. Congratulations, you have eliminated the Harbinger of Valusia without wracking up any Fury of Yig at all.