What I really want to build is a halfling that draws opportunity attacks so as to trigger his fighter friend's defender aura or combat challenge. I want to have such a high AC vs. OAs that I never get hit. I'd like the highest AC I can get for this while still remaining functional. I did some tests...hybriding into Ardent for the mantle that gives bonuses and...such. So far, the highest I can get is a 23 vs. OAs. Any ideas?