He knew how Obliviation worked. It was relatively simple as far as mind magic went—a removal of specific, targeted memories. When cast poorly, a sloppy Obliviate could be devastating. The less experienced the caster, the less precise their spellwork, the more damage they could cause. However, when cast correctly, minds were resilient; the brain reshaped itself around the hole, scar tissue filling in the blanks that remained. 