A Tale of Two Guardians [Scenario]

Based on the previous issue, it seems I need to collect all the Guardian artifacts – I'm tired of searching for them; I've only found four so far. My hero is maxed out in terms of skills. I have a huge army, but I don't know where the artifacts are.

I played this scenario quite a while ago, but I definitely remember collecting all the artifacts. I just don't remember where each one was located. I completed all the quests except for the final one. No matter what I did or how long I waited, the gate wouldn't open. And I'm too lazy to replay it.