You need to buy some Rancor off of an uber-leet Creature Handler..
Today, I saw a Master Creature Handler. I was truly amazed, but then I realized he probably played 24/7 to get there, so it really wasn't that amazing.
OMFG.. I also heard that Bestine was taking over by 2 rebels and they guarded the medical center and star port with 6 rancors.. the sad part is they were only Novice Creature Handlers are probably bought them off of somebody. This really pissed me off. I hope this gets nerfed because this is like pokemon vs player not player vs player.
If I wanted to, I could buy as many rancors as I wanted to and give all of em to the PA's CHs. But Rain doesn't want us to get rancors since they're going to get nerfed (This has been confirmed by Holocron and it will require certain lvls in the CH tree to use certain creatures). You'll be able to use a Rancor at Master CH so I'll just save it for you until you get to that lvl, eelie..