When he's in his evil siren mode,he'll start having:
Dark black wings with dark red outlines
An evil and hypnotizing singing voice
And he'll soon start to grow scales within a few seconds and starts to develop other powers.
It's up to Kathy-Chan and DJSmell to stop him.
Kathy-Chan:Where is the source of Will's powers?
DJSmell:I do not know.