Kingdom Rush Frontiers - Darklight Depths (Bonus Level) Heroic Challenge Hard/Veteran Walkthrough

The game is Kingdom Rush Frontiers, the second game in Kingdom Rush series, you can download it for cheap (under 5$) on Google Playstore and you won't regret it. My Kingdom Rush Frontiers walkthrough will feature all of the levels in the hard/veteran difficulty level.
This is the bonus level, Darklight Depths, the heroic challenge walkthrough.
Enjoy :)