When the summoning of the Memory Demon reveals that it's not only Clary's memories that have been meddled with, Alec finds himself being pushed off the path set out for him and onto a different one.

No one would help him get to the bottom of Kerberos, and it had all reached a breaking point when Iverson threatened to terminate Keith’s scholarship if he kept snooping. So Keith got what he came for, the little black book no one was ever meant to find, and stopped snooping. Because now, he’ll have someone else to do all the snooping for him. The situation isn’t ideal, Keith thinks as he slits his palm open and methodically draws the pentagram on the floor, placing the necessary items one by one into each point of the star. But considering the circumstances, he thinks he’s done alright for himself. More importantly, for Shiro.

“Most of the time, curses aren’t specifically or intentionally cast,” Alex explains. “It takes a lot of supplies, and time, and energy to set a curse. Most magic carriers won’t do it; it’s not worth it.” “If it’s not a curse…” “It’s a mutated spell.”