Need help on whether or not to remove a character or two and put them in a sequel, & thinking about adding a demonic villain that’s inside the artifact

I’m writing a story about a group of people coming together to go after a artifact that has life changing inside it that can change their lives and at the end they have grown and become a team. But im kinda stuck on whether or not i should add two other characters or not. I really want a team of 5 characters but I also don’t want to suffocate my audience with too many main characters. I also don’t know if i should add a demonic entity that lives inside the artifact and when released starts causing havoc so the main characters have to stop him. Im writing a fantasy story (I really love fantasy) I want to add what i like into my story but also want to keep my viewers in mind as well. And I also planned on having the characters in the sequel being a team and protecting others since the first story only had them going after money.

Any advice is greatly appreciated