Anthar's Advisary

You create strings of swirling black and yellow lights that loop around in the shape of the area of effect of any spell you can cast.

The lights are only visible to your allies. Any ally attempting to cross into the area hears the words "are you sure you want to do that?" 

Close inspection will reveal the words "Advisory, incoming spell, do not cross this line" made out by the lights. 

As a bonus action on your turn, you can move the lights up to 120 feet to a new spot within range. You can also optionaly change their shape to match the area of effect of another spell you can cast.