Honestly? I have no idea what the hell is going on

The Animals - House of the Rising Sun (1964)

Silver Jews - New Orleans (1994)

You are a canny adventurer, and have heard many a tale of artifacts like these that end in tragedy, either from some corruptive force emanating from them or some dickhead finding where the thing was hidden and breaking the demonlord free.

Right away we would start building 2 identical ominous tombs (vertically down to be away from people. No above ground structure) in the wilderness, far enough apart that you could get lost going from one to the other, & wilderness-y enough that for at least a few centuries they’ll only be seen by lost hunters & poachers, and farmers after that. In order to transport materials to these locations, we’ll probably have to use a road that goes to a village for each. We’d probably expand these roads to get much further away but still displace everybody living in the villages to minimise the number of humans living near to the Dark Tombs. And we’d have the villagers write (or dictate) angry messages like ‘This better be fucking worth it’ which will be important later.

In the meantime, one of the party, likely whoever sealed the demon lord in the amulet, or myself for offering this plan, would get hugely into the dark arts. Demonic arts. They would start binding demons like it was their absolute passion in life. We need so many demons that they would bicker for millennia without ever being able to join together or break away to escape. We need these demons to be crabs in a bucket, and we need them to be strong crabs. Then, I/our doomed party member binds the shit out of these guys to the location of one of the tombs, wards the bricks of that tomb against demons, and ties them to random items that go in that tomb. We put the amulet of the demon lord at the very bottom and ward the shit out of that too. Everything is as magically airtight and undetectable as we can possibly make it with our skills & the knowledge of our new mini demon lord. We also heavily ward the site with the utmost abilities of any holy guys willing to take part, but they only ward and bless the outside of the structure. The inside is hella evil and bad.

We also carve into every level instructions on how to bind the demon lord, his weaknesses, and messages about how there is absolutely nothing to gain here and much to lose. We do this in every language we know of. Therefore any future adventurers who try to plumb it for treasure will find NO treasure, only a nest of gnarly ticked-off and bored demons. If any of our languages are recognisable, they will be warned away. Any adventurers who are strong enough to make it to the bottom and find the amulet are definitely strong enough to seal the demon lord away, or have even better ways of dealing with him.

THEN we take the second tomb and super super bless it. We carve the same messages into this one and anchor / reinforce all the things used to initially bind and command the demons here. In the warded room at the bottom, we will eventually bury our mini demon lord party member, binding their soul there along with the letters of the pissed off villagers, any holy texts the holy guys who helped us wanna evangelise, and messages from us to our guy about how much they’re a good person and we love them and the blame for what they had to do in their hella dark rituals doesn’t fall solely upon their head but upon all of ours so don’t write themselves off or keep doing evil stuff now that it’s over, blah blah blah and some light reading and a few packs of cards so their soul trapped there for centuries probably won’t ferment into another demon lord lol. Also a reasonably nice enchanted amulet that has some powerful effects.

This is a decoy tomb. Anybody looking for the demon lord on purpose to free him has a 50/50 chance of getting our guy instead, and because it’s less of an annoying nightmare to get down there, our friend’s soul will probably be released a lot sooner than the demon lord. Also, finding A demon lord and A powerful amulet in a heavily warded and holy tomb in the middle of nowhere with a ton of demonic binding sigils everywhere will likely convince them they found the real tomb, it just became boring and mid with time. Truly the powers of the past Golden Age were mediocre compared to the progress of the future. And in a future where they are right AND a future where they are not, they still might give up right there.