Conversation so far:
Who was Gildas?
Gildas was a 6th-century British monk.
Why did Gildas condemn his contemporaries?
Gildas' contemporaries, both secular and religious, are condemned because he blames them for the dire state of affairs in sub-Roman Britain.

Question: What did he say about Gwynedd?
Self-contained rewrite: What did Gildas say about Maelgwn Gwynedd?