The Pursuer

The Pursuer at the Forest of Fallen Giants is an optional boss. However, this boss is on the shortest path to The Lost Bastille. The other path to The Lost Bastille would require you to journey to No-man's Wharf and defeat the Flexile Sentry. The Pursuer is usually easier and quicker to defeat than reaching No-man's Wharf and fighting the Flexile Sentry.

Rest at the Cardinal Tower bonfire and attune any spells you need for the upcoming couple of bosses. Use the Soldier Key to unlock the iron door that leads to the arena of The Pursuer. Throw an Alluring Skull to distract the nearby Hollow Soldiers to give you plenty of time to open the door. Dash to the arena of the boss.

The Pursuer is another easy boss to cheese, second only to the Dragonrider at Heide's Tower of Flame. As you enter the mist, run to the barrels diagonally to your left. Wait for the boss to perform a charged slashing attack, roll through the attack, and run to the left-most ballista. Use the ballista to shoot bolts at The Pursuer. From NG+7 onward, five bolts are enough to kill the boss. Refer to the video below for the cheese strategy.

Cheese the Pursuer NG+7, Dark Souls 2 SotFS

If for some reason the cheese does not work for you, fight the boss melee style. Buff your weapon with lightning if possible. Lock onto the boss and bait the charging slash attack. As the boss charges at you, dash to your right, strafe behind the boss, and get in one hit. See the video below for the strategy.

SL1 The Pursuer, Dark Souls 2: SotFS

Defeat The Pursuer and interact with the crow nest located at the back of the boss arena. You would be transported to The Lost Bastille.