In the season one finale, he tricks Hiccup and Toothless into being captured by Alvin the Treacherous, but later appears to regret his actions and helps them break free. During the escape, he falls from his dragon and appears to be captured by the outcasts, but it is revealed that all his actions were merely a ruse to learn about dragon training to help Alvin.
- Mildew Becomes One Of Hiccup's Enemies During The Adventures.
- Mildew Now Accompanied With Alvin The Treacherous, Dagur The Deranged, And Savage.
- Mildew Mostly Have A Partner, Lord Shen
- Every time When Mildew And The Villains Are defeated And Sees Hiccup And The gang Victoriously won, He ended Up Shouting, "You'll Pay For This!!!" To Them.
- Mildew will become Jaden and Jeffrey's enemy in Jeffrey, Jaden & Hiccup gets Spirited Away.
- He's also Dr Hutchinson's Enemy as well.