TITLE:An Approaching Terror - The Citadel of God, "The Ark Cradle" is the one-hundred and thirty seventh episode of Yu-Gi-Oh! 5D's.
DESCRIPTION: After a long fight, Yusei wins his duel against Aporia, causing Team 5D's to become the the First Time Champions of the WRGP. Yusei and co. thinking they have been able to protect the peace of New Domino City by having beaten Aporia. Just as things look peaceful , the sky suddenly shatters and the Ark Cradle appears causing the city to fall into a massive panic.
Yusei and the gang are confused, surely because the Ark Cradle was supposed to disappear if Aporia was defeated. Shaken by this turn of events, they learn a frightening new truth no one could have expected.