Map awareness is one of the most important skills in DotA 2 and map vision/control is a powerful tool that new players often forget to use. Additionally, new players tend to get stomped quite easily by invisibility heroes as they do not know how to deal with them properly.
I would recommend creating a tutorial that specifically explains:
- Day/Night vision
- Fog of War
- Tower vision
- Low/high ground vision
- Invisibility detection
You could, for instance, let players play as Sniper, scouting a battlefield littered with dead bodies and destroyed buildings on fire, placing wards and looking around trying to find the mysterious cause of this mayhem (with the help of Roquelaire) until the players eventually spot and hunt an invisible Clinkz using a sentry and Dust of Appearance.
The reward for completing this tutorial could be a custom ward.
Here are some of the best locations for this new tutorial:
3 is the best location IMO. The tutorial could appear right before "5 Practice Matches Versus Bots" which is exactly when the player may need to know all about map vision and warding. It would be located in The Hoven, home of Clinkz. It would thus make sense to include Clinkz as "the invisible killer" in this tutorial, both from a lore perspective and from a design standpoint.