Well I didn't really expect Juvia to die, so it's not a surprise she pulled through and Invel should have put up more of a resistance. Maybe he might retaliate a bit in the next chapter, but I doubt it. It was however nice how Gray dealt the final blow, it was reminiscent of how Natsu beat Zancrow by being able to absorb their magic and then use it against them.
Most intriguing part of course was Gray finding out who END is. Until now I never really felt there was a particular reason that it was going to result in Gray vs END. Despite the fact that they have opposing magic types and a rivalry going on, I never thought that their relationship was that prominent for it to end up like this. Either way this means that we might finally see the revival of END.