Hopefully they'll explain it, not sure if the anime will bother with it though. As for Merciless, I recall it serving another purpose in the LN other than the instant kill-all, it was a bit more nuanced use, but we work with time constraints, don't think it matters much in the grand scheme of things. But I don't recall the details all that much, so I may be misremembering.
Seemed like they were lackey's for the "main" demon. I also wonder if they die or do they just get "unsummoned". Very curious on that regard.The demon sacrifice was also weird. "Hey, these two are happy to die for you"... "Oh I'm so envious"..
1) you could have offered yourself if you're so envious.
2) it'd have been better if the demons themselves offered.
3) it's a bit weird for Rimuru to be so ready to accept the Demon's offering. Imagine if Benimaru said "Take my life". Rimuru wouldn't say "Oh, okay. Just what I needed."
-This assumes demons "dying" is permanent and not some "return to Hell until the next summon"
Unless there's a more distinctive meaning in Japanese, it's a shame that we have DEMONS and then we have DEMON LORDS, and apparently there's no relation between each other. Makes it quite confusing to tell what's what in this world.
Also, the Demon Lord gifts were handed out before the resurrection, so wonder if Shion got a gift or not.
I don't think it was Rimuru in the end calling the shots, I think it was the Great Sage (Raphael now) controlling Rimuru. I'm not sure if that skill was able to do that before. I recall it interfering with some aspects of Rimuru before (like preventing him from getting drunk and such), but to take control of the body and make decisions as well is very a very curious development.
I'm also not certain on who was making the decisions while evolving. Like Great Sage was improving itself by its own volition, sacrificing things to improve itself without Rimuru's input? I think the only time during the evolution that Rimuru himself asked for something was to evolve Gluttony, but Rimuru himself has left things from time to time up to Grate Sage before if I recall correctly, so it may very well be just that.
In any case, I found it to be an interesting dynamic. I got Skynet vibes...