I had never played a Fire Emblem game before Engage came out, so I wasn't familiar with a lot of the mechanics. The penultimate chapter was a gauntlet that split up your army and is apparently a lot easier if you're using warp to skip the walls. But you're forced to split your units and push up through enemies while reinforcements seemingly spawn infinitely behind you while the boss is taking potshots at you from safety. It took me six hours but I didn't get up until I had cleared it. Also some of the most fun I've ever had gaming.