Heya! Ok so you are trying to get Efreet, no? Well yes you're going to have to defeat him alone. First off you need to make sure you have a good critical, power, good resistance. You're not allowed to have any blades or traps or shields( yikes!) You just have to strike him with true, hard core power. If it helps, get some tc to help you. If you have a pet that heals, use it. My advice is to knock out that minion first.
Someone said that you could put a marker inside the instance, use a potion, and quickly teleport back, but if you look for mana wisps or health wisps, it will reset. I'm not sure if this works or not, I just read about it.