It also hurt Rock's mind in every tense. But that was Ham's secret challenge: Make Rock and Odium think through all of the tenses, and then measure how successful they were, how fast they were, and how much their brains hurt at the end. (And in which tenses.) They were almost tied, but Odium, being a Shard and having much more mental capacity than Rock, didn't have a headache, so he won.