Ditko's final year on Doctor Strange is some of his best work ever, 10-page segments of pure magic every month. "Beware...! Dormammu Is Watching" is right in the heart of that run, a great chapter in the saga. As Strange returns from his quest for Eternity, he finds that Mordo, working for and powered by the Dread Dormammu, has taken the Ancient One prisoner. What follows is an epic magical battle, while Dormammu, the Ancient One and the as-yet-unnamed Clea look on, amazingly drawn by Ditko.
As you can see by the choice of close-up scans, one of the things I love about this story is the way Ditko would draw hands, especially of anyone engaged in casting magic spells. I don't believe in magic, but I know in my heart that if it did exist, it would have to be accompanied by hand gestures straight out of the Ditko playbook.
Lots of other classic Ditko bits in this page, from that weird hair on Clea, and the worried look on her face to the disheveled hair on Doc in the last panel. I think I even catch a hint of a Ditko sneer on Dormammu in the third panel, and that's an impressive thing to manage with that character design.