Defeat the Old Ones

Brightstone Cove Tseldora

SL1 The Duke's Dear Freja, Dark Souls 2: SotFS

The Duke's Dear Freja

You should be able to one-hand the Rapier now while holding a torch. With the torch in your left hand, Freja's spider minions won't attack or approach you, allowing you to focus solely on Freja itself. Buff the Rapier+10 with Charcoal Pine Resin, be far enough away from Freja to bait the laser attack, run to the other head (the one that isn't firing the laser), and attack this other head. Rinse and repeat until the boss is defeated.

Complete Tark's quest line, Dark Souls 2: SotFS

Defeat Freja, proceed to the Lord's Private Chamber, and kill Duke Tseldora to collect a Fragrant Branch of Yore. Light the Primal Bonfire and use it to warp back to Majula. Have at least 72,000 souls to purchase Brightbug x 3 from Melentia. Exhaust Tark's dialogue to receive a Fragrant Branch and other items. Save these two Fragrant Branches for Aldia's Keep, where they will be used to farm Bonfire Ascetic and Elizabeth Mushrooms.

Lost Bastille

Fragrant Branch of Yore at The Lost Bastille, Dark Souls 2: SotFS

Start from the Tower Apart bonfire. You will find an iron chest, approaching which would spawn the Pursuer. Defeat the Pursuer for a Twinkling Titanite and collect a Fragrant Branch of Yore from the chest. You must defeat the Ruin Sentinels to open the passage to the Bastille Key, which is required to open two doors that block your passage to two giant oil lamps. Lighting the lamps would increase the visibility during the fight against The Lost Sinner.

SL1 Ruin Sentinels, Dark Souls 2: SotFS

Ruin Sentinels

The Ruin Sentinels are weak against lightning. Buff your Mace+10 with Gold Pine Resin (if you have any) or infuse a Mace+10 with a Boltstone. Equip the Peasant set (excluding the Peasant Hat), the Mad Warrior Mask, and the Vessel Shield to increase your Adaptability to 15. Equip the Silvercat Ring to reduce fall damage as you enter the boss arena and when you drop down from one of the platforms in the boss room. Enter the arena and your character would be dropped onto a platform. You want to remain on this platform while fighting the first two Sentinels. Strafe around the first Sentinel and get in one or two hits. Sometimes the Sentinel would drop down to the floor. Wait at the edge of the platform for the Sentinel to jump up onto the platform again. The longer the fight drags on, the more Ruin Sentinels would join the fight. Get rid of the first Sentinel as quickly as possible and wait for the second Sentinel to spawn and jump up onto the platform. Rinse and repeat the above strategy. When two Sentinels are in the arena, drop down to the floor to allow yourself more room to manoeuvre and evade attacks. Patiently wait for an opportunity to get in one hit.

Location of Bastille Key, Dark Souls 2: SotFS

Defeat the Ruin Sentinels and light the Servants' Quarters bonfire. Navigate through a corridor to open a door and turn left to grab the Bastille Key.

Sinner's Rise

Two locked doors are found in front of the boss arena. Use the Bastille Key to open the doors and light the two giant oil lamps to increase visibility within the boss room. Before fighting The Lost Sinner, ensure you have purchased all Brightbugs from Melentia.

SL1 The Lost Sinner, Dark Souls 2: SotFS

The Lost Sinner

Buff the Rapier+10 with Aromatic Ooze or use a Rapier that has been infused with a Faintstone. Equip these for 15 Adaptability: Peasant set (excluding the Peasant Hat), Mad Warrior Mask, and Vessel Shield. Roll through the boss' attacks, position your character behind the boss, and get in one hit.

Defeat The Lost Sinner, collect a Fragrant Branch of Yore, and light the Primal Bonfire. If Aldia spawns, exhaust his dialogue to follow his quest line and have him be the final boss. He is an optional final boss. Don't interact with Aldia if you don't want to fight him. Warp back to Majula. Have at least 108,000 souls to purchase Brightbug x 3 from Melentia.