Learn Turkish: Güya hâlâ canavarları püskürtüyormuşmuş! - He claims to be still repelling monsters!

This is the compound inferential of disbelief, which is the focus of this lesson. Adding a second -muş to the reported present tense (-yormuş) adds a layer of heavy sarcasm or mockery. It basically means 'he claims he is repelling them, but I definitely do not believe it.'

Does güya always have to be used with the -mIşmIş suffix?

No, you can use the double -mIş without güya, and you can use güya (meaning 'supposedly' or 'allegedly') with normal verb tenses. However, they are frequently paired together to amplify the mockery and make the speaker's disbelief absolutely clear.

Where does the verb püskürtmek come from?

It is the causative form of püskürmek (to spray, erupt, or spew). By adding the causative -t, it becomes püskürtmek (to make something spray away, or to drive back/repel). It is commonly used in contexts like repelling enemy attacks or, in this case, monsters.

Why does canavarları take the accusative suffix -ı?

The verb püskürtmek takes a definite direct object when referring to a specific group. Even though the English translation just says 'monsters', the Turkish accusative indicates that these are specific monsters already known in the context of the conversation, rather than just any monsters in general.