Critical Focus

3rd-level divination (Ranger)

Casting Time: 1 bonus action
Range: 90 feet
Components: V
Duration: Concentration, up to 1 minute

You choose a creature you can see within range and focus all your energy on its weak spots. Until the spell ends, your critical hit range while making a melee weapon attack against the chosen target is extended by 1 for the duration of this spell (so rolling a 19 also counts as rolling a critical hit).

Also, whenever you score a critical hit against your target, the critical hit range is extended by an additional 1 until the spell ends.

At Higher Levels. When you cast this spell using a spell slot of 4th or higher level, you choose an additional creature when casting this spell for each spell slot above 3 (a maximum of 3 additional creatures).