Kamen Rider Build, Episode 20: "Devil Trigger"

[Toku Prime]

Wait, a black version of the main Rider that's not a separate villain character?​

This week: Stalk won't tell us what his ultimate goal is (I sure hope the writers know, at least), the counter-invasion of Hokuto begins (but doesn't get very far), Misora uses her powers in a useful way, Gentoku goes Rogue, and Sento pulls the titular trigger.