There are going to be times when no matter how high your defenses are you’re still going to take a few hits. Whether you’re the nimble striker who opts for mobility over heavy armor or the defender who marks opponents to intentionally draw attacks away from others, all PCs eventually get hit hard. Luckily there is a relatively easy way to reduce the damage from some of the hardest hits that deal the most damage – energy resistance.
A disproportionate number of powerful monsters deal more than just straight-up, every day, normal damage. Many deal energy specific damage. So when you’ve done everything you can to raise your defenses and you still find yourself getting hit and taking an obscene amount of damage, it’s time to find magic that provides energy resistance.