Deep under the Yahar'gul Chapel is the Hypogean Gaol - you may have find yourself here after dying at the hands of a spectre much earlier in the game. Through the cave entrance at the back of the prison is a vicious monster: Darkbeast Paarl.
If you were transported to this area early on, Paarl would have been pretty tough. But if you've fought the bosses in the order of this guide, he'll be a cinch. His main attacks are claw swipes, easily avoided with a sidestep. Thanks to his lanky structure, you can even roll directly under him to dodge. The only tricky part is actually striking him - unless he's stunned and toppling over, you'll have to aim for his limbs.
After doing enough damage, Paarl will power up, adding bolt damage to his attacks. Continue the same dodge strategy, but be aware that at a medium to long range, he'll also chuck bolt orbs (also avoidable via a sidestep). Attack Paarl in between his own blows, and you'll take him down - opening a handy shortcut back to Old Yharnam! - in no time.