Sword Barrage

You conjure a magic staff to your hand that remains for the spells duration. The staff appears as a metal rod with a full length crystal sword on the head. If you let go of the staff, it disappears, but you can conjure the staff again as a bonus action. When you cast this spell, and when you take an action to do so on subsequent turns, you use the staff to conjure arcane swords made from force that appear through portals around you. Three portals open as a arcane sword flies out from each. You direct all arcane swords to a creature you can see within 90 feet of you with the staff.  Make a ranged spell attack against the creature for each sword. A sword does 3d8 force damage.

Lastly, all these attacks score a critical hit on a d20 roll of 19 or higher.

At Higher Levels. When you cast this spell using a spell slot level of 8th or higher the staff creates an additional portal.  If you cast this spell using a 9th level spell slot attacks from this spell score a critical hit on a d20 roll of 18 or higher.