Acceleration Sphere

You channel your internal magic, causing time to disrupt around a point you choose within range. A 15 feet radius sphere is created at the target location. The sphere is coated in a shell of energy that pulsates along the outside of it, but is otherwise transparent.
Creatures that start their turn in the sphere have their speed doubled, gain a +2 bonus to AC, have advantage on Dexterity saving throws, and gain an additional action on each of its turns. That action can be used only to take the Attack (one weapon attack only), Dash, Disengage, Hide, or Use an Object action.