Miroku is an itinerant monk and colossal pervert. Despite the drubbings he gets from Sango, he's probably the most powerful member of the "gang".
First off he's got the Wind Tunnel (aka Kazaana, 風穴) in his right hand. The Wind Tunnel is the result of a curse placed on his family by Naraku. Miroku's grandfather, who was also a monk, was one of Naraku's early enemies. Though Naraku always took a different form, Miroku's grandfather was able to identify him and fight him to an apparent stalemate. For their last fight however, Naraku adopted the form of a beautiful young maiden. Miroku's grandfather being lecher as well was distracted by Naraku's facade long enough for Naraku to pierce his hand and inflict the curse on Miroku's paternal line. Miraku's grandfather's wind tunnel grew each year until it engulfed him, as the wind tunnel in Miroku's father's hand. Miroku then inherited the Wind Tunnel himself and the only way to stop it from growing each year until it engulfs him is to kill Naraku. In the mean time, the Wind Tunnel is an insanely powerful weapon. Like a black hole it sucks in anything and everything to be destroyed unless it's covered by Miroku's Buddhist Sutra beads. The only thing that seems to have any effect when it's sucked in are Naraku's Hell Wasps (Saimyoushou) , which sting and poison Miroku on their way in. Aside from those, he's sucked in trees, cows, and buildings with no ill effect.
Aside from the Wind Tunnel he has a fairly varied arsenal of priestly powers, including force barriers, super-speed, and the ability to make "bubbles" of invisibility to evil creatures.
And none of that works, he can just hit stuff with his Shakujou (monks's staff), which is what ends up doing about half the time anyway.
In our first exposure to him we find him exercising a weasel demon from a statue to free a nobleman's daughter from its influence, only to use that as a cover to clear out the nobleman's house of treasures. He then laments the low price he got for pawning all that stuff.
