I... can't go on...
Fallen Sentinel is a miniboss and a Spirit.
Fallen Sentinel is found at the far left end of the site, at the top left of the "Bastion Gate" Respite.
Battle
When fighting close range, Fallen Sentinel swings his sword. If Lily stands behind him, he can perform a spinning attack that reaches both above and below.
In medium and long range, he can conduct a dashing attack while thrusting his sword. Using a different variation of this attack, he teleports to the same altitude as Lily before dashing and whirling, dealing additional damage.
On NG+, he can swing his sword twice instead of once. Both of his dash attacks contain a spin, and when he teleports, he moves to an even lower spot, making the attack impossible to evade by just crouching on the ground.
Spirit
Fallen Sentinel spirit flies far forward from Lily, dealing harm to enemies in its route.
On levels 1-3, damage scaling is 150%.
Starting at the fourth level, the Sentinel spins as he travels. This move deals 5 instances of damage, one with a scale of 130% and four with a scaling of 10%.
The spin alters slightly at the sixth level, with one instance of 140% damage and seven instances of 7.5% damage.