If they will kill you for being a mortal, then why don’t you try and gain immortality?

So I take it Shiden doesn’t ever play tactical or strategy games?
All he needs to do is think how they will try and kill or betray us in a theoretical situation they are immortal
They have never been pushed to the extreme they know their predecessors we’re hung by their own arrogance but they have never been pushed to the point where they might be in trouble and as Shiden pointed out they would rather “Kill us” then bargain
So all they need to do is point out that one they would be fighting alone they would be fighting against the Null the Magi and whoever else and so on to get them to talk and then it’s just a counter of what would I do if one I was immortal controlled both Life and Death and hate this people so much I would kill them and what would it take for them to to get me in front of them to talk on top of that all he has to think about is what would they do to insure their safety as well as what they could set up for counter attacks and plug that up.
at least that’s what I think