The B'dra is the end result of Klingon experimentation to produce a heavy
assault version of the B'rel Bird of Prey hull. A heavy photon torpedo system
takes up a large part of the command boom, and half the disruptor armament
was sacrificed to power it.
While the Klingons appreciate the range and hitting power of the heavy
photon, the ship is usually forced to cloak while its weapons recharge or
face destruction by a retaliatory strike. This does not stop Klingon
admirals from deploying these ships when alpha strikes are important and a long
battle is not expected.