Can you tell some requirements for it? Does it require certain amount of immexp?

I have 1500 immexp and more than 25000 exploration exp, took no edges and still dont have it in the list.

You mention explore xp, but I don't think that helps with edges. You get mv for those. It's obvservation xp that helps with edges. So I've been led to understand.

Equally. Sometimes I have gained just exploration xp with no observation, and gained edge points the same as when I've gained just observation without exploration.

What level are you? It's not available very low.

Also, it's not a cheap edge.

I am hero. I have ehren soul long ago. Got 500 imm exp + lots of exploration exp from that time

It was broken and not showing up at one point. Might be one of those code changes that weren't effected by the downtime.

From my experience it did have an imm exp trigger. I want to say it was 2500-3000 imm exp. Once I had that I was able to take the edge twice with my observation experience.

Looks like you are right. I took four edges and still had Ehren Soul in my list, it disappeared only on fifth edge.

Can IMMs confirm this?