Going by memory, they sealed Amalet away with 'the rest of our horrific inventions', something along those lines.
I believe the timeline is:
Zhamla doesn't want to be a Collector.
Zhamla is given a crown by his friend. This does nothing.
Zhamla is bullied into being a Collector.
Tessen wants you to go find the crown she hid when she was young. You dig up the crown... but it doesn't really look like the one she gave Zhamla as a child.
Zhamla wears the crown and gets an immediate adjustment of personality.
Zhamla goes around collecting various artifacts and all the cards.
Zhamla comes home. Disaster.
Zhamla leaves to hunt his final card.
Machines are made to combat Zhamla. He destroys them. (He might not actually have Amalet at this point. They may have put Amalet in Gundam to fight him, he won and claimed Amalet?)
Zhamla is tempted home to rescue Tessen, who he believes to be in trouble. It's a trap.
You arrive. The priests cast a sealing spell on Zhamla.
Zhamla is stripped of his artifacts and banished or seal somewhere in the world. He's not dead.
Five are captured and scattered around the world in heavily protected areas. This is where Amalet is locked in the Flying Fortress. (How did Gaantlet get in the Season Temple, though...?)
One escapes...
If my theory is right, Bag had aspirations to get the gang back together long before your mom got roasted. So whatever he's up to, it's possibly not about revival. It could be they have nothing to do with reviving anything. So what does Bag want to do?
A) He wants to break the seal on Zhamla to complete the original mission. Human card!
B) He wants to break the seal on Zhamla because he knows Zhamla isn't evil, Bag was with Zhamla before Zhamla got the crown along with Braazlet.
Or C) has he forgotten his childhood? We've seen from Gaantlet and Ivy that the artifacts have trouble remembering their youth a thousand years ago. It could be he honestly doesn't remember any of it, or the sealing spell sealed all their memories and stumbling across Zhamla's sword in the dragon cave was a huge coinidence.
It seems extremely suspicious that the five artifacts that were with Zhamla are coincidentally the exact five needed to ressurect someone. Especially since there was shown to be nothing special or sinister about Braazlet. We also know there are more than just these six artifacts in the world, Marino talks about his family's collection and Ivy shows off hers. There's also Shiidu, who has nothing to do with ressurection.
Or maybe there's a legend that the five artifacts can ressurect someone... but Bag has forgotten that the only person they can 'ressurect' is their owner, sealed wherever he is.