zimberzimber
Terrarian
It's not a must, you can ask them if you want to, but otherwise its a great tool that would help you advance further in moon invasions and help early hardmode players with these kinds of event.I think that an NPC that help you fighting should be desnecessary. Would be a cool addition, but I don't think that fighting your side would be a good addition. Like... it would help as nothing, or help as god! What I want to say it's like that would be so much desbalanced, and would bug a lot. But logically, if they put it without making any of these things, it would be very very valueable.