The Trap Door Sezon 1 Odcinek 6: Creepy Crawly

Something large and black with "lots of legs" comes out of the trap door and scuttles off down the corridor, but Berk won't believe Boni. He goes in search of it and finds a tiny spider, thinking it must be Boni's monster, but just then the enormous black spider drops down in front of him, wraps him in thick green web and chases him into the kitchen. Drutt spins the spider up in his own web and Berk is able to push it back down the trap door.