i don't have friends, nice bait though with title. good job
To be clear, if you do this, you will get the recipe for the next level sigil after the one you did with your friend. Sadly, you can't get ported in at the last minute to, say, a T10 and get all the intermediate recipes. You'll get T11 only. But you will get the title and the achievements. The best thing to do is have your friend bring you into a T1 and then carry on by yourself, assuming you can beat T2.