I Sacrifice, Therefore I Am (Was)

Question: From what I understand, sacrifice to the Aztecs is an important part of maintaining and powering the universe. How do they react to pantheons like the Celtic ones, for whom sacrifice is a matter of simple veneration? Do they see it as needless luxury, or out-and-out blasphemy (since the other pantheons aren't actually being powered up by sacrifice)? A betrayal of their people? Or would they be fine with it?

A lot of this will probably depend on the specific Aztec god in question, so we're going to give you a few different approaches and let individual Storytellers figure out which one would make the most sense to any given god of the Teotl.

If you're talking about a Teotl god who isn't particularly bright, who hasn't had much interaction with other pantheons before, or who just has a poor grasp of the occult or a healthy opinion of how important and universal his own pantheon's practices are, there may be no conflict at all. Gods are, at their hearts, pretty much all egomaniacs, and those who are community-focused like the Teotl tend to extend that to their entire culture - i.e., Mexicans are best, everyone else probably does exactly what we do, because why would they ever do anything else? Under such an interpretatio mexicana, some Teotl may simply assume that other pantheons are getting power from their peoples' sacrifices. That would look normal to them, and if they're not particularly good at understanding how magic works, it may not occur to them that those other pantheons have different powers instead or that the entire universe doesn't run the same way that it does for them at home. Those gods probably totally approve of bog-body sacrifices or mummified mountain sacrifices; to them, those are the only other pantheons who are being even vaguely responsible. In fact, they probably severely dislike, or at least look down upon, pantheons who don't practice human sacrifice, because to them it looks like those jokers are just a bunch of gods being assholes and refusing to help prevent the entire universe from falling apart. What dicks.

On the other hand, those who have interacted with other pantheons a decent amount and understand that they don't get any power from their worshipers' sacrifices may have mixed feelings. Mortals giving up their very lives in sacrifice to their gods seems like it's right and familiar - after all, to the Aztecs, that's what they're supposed to be doing and it's hard to not automatically accept that. But at the same time, the Teotl are deeply invested in and loyal to their people, divine and mortal alike, and wouldn't dream of hurting them if they could help it (certain shining malcontents like Tezcatlipoca aside). It's the fact that the community of the Aztec world is so loyal to one another and the greater good of all that makes the deaths of its members a sacrifice at all. So from that perspective, some gods might see it as a rather unforgivable abuse of worshipers. Killing off some of one's worshipers to make sure everyone in the universe doesn't die is a noble sacrifice, putting the needs of the many before the needs of the few, but killing them off for no reason at all is being straight-up disloyal to the very people you're supposed to be taking care of. Gods coming from this point of view might be shocked, appalled or even furious with deities of other sacrificing pantheons, who they might see as being massively irresponsible or oppressive to their own people.

Of course, it's also a pretty entrenched idea among the Teotl (or at least the mortals that worshiped them) that the Aztecs are in fact the best humans in existence and every other people is lesser and therefore existing only to be conquered and/or sacrificed for the good of the world, so they may not be that upset about it. I mean, it's unfortunate that those other pantheons are jerks to their constituents, but their constituents are clearly not as important as the Teotl's constituents, so it can only be so much of a tragedy.

And finally, there may be some Aztec gods who simply don't care at all what other pantheons are doing. Especially if they realize that other pantheons can't get power out of sacrifices, they may just shrug and go on their way, probably with a side order of shaking their heads and talking among themselves about how only they are really doing anything to help the world not slide into destruction and it would be nice if those other, obviously lesser gods someday learned to do the same. They might see mortals practicing sacrifice anyway as being well-meaning but ultimately pointless and not really care about it much; it might also be a popular opinion that those other pantheons are obviously crippled or sub-powerful in some way, because their worshipers are doing it right but for some reason their gods just can't seem to benefit from it the way they're supposed to, which probably means something is wrong with them. Or, perhaps some might hold the theory that other races of mortals lack sufficient amounts of chalchiuatl, the precious water and source of energy carried in blood, and so killing them just isn't as helpful as killing an obviously much more important Aztec person would be (although this theory is probably held more by homebody gods, as any Teotl who go jaunting abroad will find it just as easy to murder and Australian or Tibetan person for Legend as they would performing a sacrifice at home; and ancient Aztecs definitely did sacrifice members of other ethnic groups they encountered, so maybe this is more of a people-who-aren't-Mesoamerican-are-inferior kind of thing instead of specifically Mexica-only). I mean, if you kill someone who isn't Aztec and therefore doesn't matter to your Loyalty- and Duty-bound view of the world at all, was it really a sacrifice?

The one thing in your question I would say probably nobody thinks is that those other pantheons are indulging in a "luxury". If the sacrifice literally doesn't do anything, it's not really a luxury at all - that would be like buying a box of literally nothing, and then claiming that this was a "luxury" that you kept in your house. One possible approach might be that other pantheons are just so powerful that they don't need sacrifice to keep the universe going and therefore sacrifice could be considered an unnecessary luxury... but I doubt very much you're going to find many Teotl who are all about deciding that everyone in the world is more powerful than they are. No pantheon is in ever in favor of that kind of interpretation.

So really, it depends on a particular god, how much your story has them gallivanting around the world and what sort of personality and idea of the powers of various pantheons they already have. Someone like Quetzalcoatl, who probably understands other pantheons' practices pretty well and doesn't like killing people to begin with, might be horrified by such blatant destruction of people for no reason at all; someone like Tezcatlipoca, who is completely happy with murdering people if he thinks it's funny, probably has no problem with it at all or is amused by how stupid those other pantheons and their inability to get power out of such actions are; and someone like Huitzilopochtli, who is likely none too bright and fully invested in how important and powerful he and his people are, probably assumes that everyone else also does it his way and would have no concept of gods who were receiving sacrifice without also receiving power. Mix and match as necessary.