As you may have noticed, the Fett is one of my favorite characters and I got his expansion without the twin shadows, due to limited capital for gaming. I am very interested in playing him in the core campaign but I want to be sure I am allowed to. Is there an easy way to tell if I can play certain Allies/Villains in certain campaigns, I read the rules and I noticed the Roman numerals on the side of the card but they seem to all intertwine? Long story short, I am confused.

Boba Fett's agenda set has time period range of 1-5 so it can be included in either current campaign. (Core campaign is time period 3, while Return to Hoth is time period of 5.)

(To earn Boba Fett to be able to choose him in your open groups needs that you come across his agenda mission, buy it and win it.)

You'll have more probability to get to play with Boba in the Twin Shadows minicampaign (and win him as a villain).

You have to win him as was said, but he's pretty pricey. If you really want to play him he's not going to be doing you any sort of unbalancing favor by taking him so you might be able to convince your players to let you play him without winning his agenda mission first.

You can always play him in skirmish.

Thank you both, I appreciate it!