Throne of Want

In case you have already defeated the Giant Lord, then after defeating the Throne Defender and Throne Watcher you would be thrown into the fight against Nashandra. If that is not bad enough, in case you have been following Aldia's quest line, then defeating Nashandra would throw you into the fight against Aldia. The Throne of Want can therefore be a three-part boss gauntlet. The first part is the Throne Defender and Throne Watcher. The second part is Nashandra. And the third part is Aldia. To make the battle at the Throne of Want less of a gauntlet, ensure the Giant Lord is alive and defeat the Throne Defender and Throne Watcher now. The fights at the Throne of Want isn't as insane as it sounds. Having defeated the Throne Watcher and Throne Defender, if you're then forced to fight Nashandra you can simply let Nashandra spawn and use a Homeward Bone to return to the last bonfire at which you rested. Take your time to prepare for the fight against Nashandra.

Throne Defender and Throne Watcher

76. Throne Watcher and Throne Defender, Dark Souls II: SotFS

Both are weak against lightning. Fight this boss prior to defeating the Giant Lord. Doing so would mean that this would not become a two-part (and possibly three-part) boss battle. Each of the Throne Defender and Throne Watcher can revive each other. When either one is defeated, they would kneel and wait for the other to revive them. Concentrate on dealing equal damage to the bosses, ensuring that their HPs are always roughly the same. That way, once you have dispatched of a boss, you would be able to quickly defeat the remaining one. Summon Benhart and/or Head of Vengarl as distraction during the fight. Note that summoning Benhart, and have him survive this particular fight, doesn't count toward his quest line.