bladed hoodwink

At a certain location you lay out a thread, and anything that touches the thread will have a blade shoot out and deal 1d10 +2 damage. When it is activated you will know as you will hear the sound of a sword. once activated the spell cannot be undone until activated. Ignores AC but you can roll de save to dodge. level 1 - 2 = 1d10+2. level 2 - 6 = 2d10+2. Level 6-10 = 3d10+2. level 10-15 = 4d10+2. level 15-20 = 5d10+5