A Warding Guide: Placement and Responsibility.

Introduction taken from this thread: http://forums.heroesofnewerth.com/showthread.php?t=4839
Written by S2Nome.

Wards of Sight
200 gold (4-5 Creep Kills)
6 minutes duration
2 charges

Wards of Sight are the single most powerful and cost-effective item in the game. If uncountered, they are the equivalent of hacking. No other item is as strong as this. As of right now, there is no limit to the number you can buy--in addition, they will not be revealed by players with Bound Eye.