This is an interesting ability. It’s main audience is the pro players and top players.
How to use?
Use this ability to prevent escapes in planned battles, predict ganks, prevent ganks, counter ganks, And general learn to watch the minimap.
This ability’s only problem is that it isn’t spammable enough and the stage it is not attainable in the stage it needs to be used for.
In honest truth, it needs to be gained as a First, second or third ability not as an aghnim’s scepter. It would be more useful that way. It’s meant for the beginning of the game for real.