Initially one appears. After defeating it, two will appear at once. Be wary of the poison water in the middle of the room.

You may find it easier to run around without targeting, then hit them after they perform their clearly projected attacks.

Bide your time until their sword glints and they perform a lunge attack. Then dodge and hit them.

They can also do a double sword swing attack that transitions into a lunge attack.

Even though there’s two of them, they’re fairly respectable and take turns attacking you.