By the way... Spoiler for the hidden boss!
For anyone struggling against the Seere (the optional Otherworlder), I've found two safe spots, for each of its phases.
For the first phase (when the Seere is on the left pillar) with orbs shooting everywhere attack, you can duck in the middle left part of the altar, around here:
All orbs will normally miss you, except one, who will spawn exactly where you are, so keep attacking to destroy it. It won't work for the other attack, where all orbs are firing vertically, except for one shooting horizontally.
For the second phase (when the Seere is on the right pillar), you can pretty much stay next to the left pillar:
From my experience, as long as you really stay next the pillar, all its attacks should miss you. Be careful, if you turn around, the character will move a bit to the right and can be vulnerable. What I recommend is to keep walking to the pillar while the creature is attacking, and when it stops, turn around, shoot as many arrows as you can, and then walk back to the pillar when the next attack triggers.