Chill Trebuchet

You evoke a mighty Ice trebuchet, swirling up from the frozen ground. This siege engine stands 50ft tall, requires a 10foot cube of empty space and is fixed in place. While concentrating, as an action on your turn you may launch the frozen blocks at any target you can see. Make a ranged spell attack, on a hit the target takes 3d12 cold damage. Buildings and vehicles take an additional 3d6 bludgeoning. While concentrating your movement speed reduced to 0ft. 

You may up cast this spell adding 1d12 and 1 minute to the spell duration for each level above 3rd.