Evil Eye

Its 20% damage bonus applies directly to the last foe that defeated you.

Use it when

Equip it for a rematch when one known foe or Guardian ended the previous night.

Limit

It adds no damage against other foes and loses purpose after the targeted obstacle is overcome.

If it is absent

Use Knuckle Bones for a broader Guardian bonus when the previous defeat is not the only problem.

When to replace it

Keep it while its condition supports the current route, then replace it when another keepsake solves a more immediate constraint.