The Barov Peasant Caller is a rewards item for the Last Barov quest. This item binds when you pick it up so it cannot be sold, and you cannot buy it on the AH. The quest requires level 52 and is a part of a quest chain.
You get it for delivering the head of Alexi Barov. You can find Alexi Barov in the camp to the left as you enter Tirisfal Glades from Western Plaguelands.
The item has a 10 minute cool down, so you will want to have it in your rotation cycle and not as your main one. The Barov Peasant Caller will summon 3 peasants to fight for you. The peasants will be a random race/gender. They will last for about 20 seconds, have about 700 HP and only hit for like 50 but they basically stop spell casters and scare the shit out of people in duels.
One nice and very cool thing you can use it for is to hide or stealth in a low level zone and watch as the 3 of them rush in and take out a single or even a party of lowbies. It will seem like a random elite mob spawn.
Also you can use it to gives you time to heal, dot, nuke, or run away.
The big plus of this summon item as for all the other summon items is that you can get it quite simple by your own, and this is a fairly good item to have if you don’t want to invest a lot of time to be able to summon some help when needed.