After you get Super Missiles in Ridley's domain, you battle Ridley himself.

Defeat Ridley

Ridley can be hurt by Missiles and charged shots.

Whenever Ridley lands on the platform, he will rapidly shoot fireballs at you. If you're far away from Ridley when this happens, crouch. Otherwise, stand at normal height. Then rapidly shoot your beam to destroy the fireballs that Ridley spits out.

Try to always stay on the end of the platform that is farthest away from Ridley. When Ridley flies up, shoot the large fireballs to destroy them. Crouch into Morph Ball whenever Ridley swoops down, and get behind him.

When Ridley starts to swing his tail in a circle and lash it at you, use Morph Ball and get behind Ridley immediately after his tail goes forward toward you. When Ridley stabs his tail down on the platform, get behind Ridley as soon as his tail has gone far up enough for you to safely go past with Morph Ball.

After the battle, there will be a cutscene, after which you can leave Ridley's domain.