PLUS ONE ABILITY, PLUS ZERO SLOTS

The idea for a new ability came to me while I was pondering network security. Lay down a wall of fire that lasts a short time and only you can pass through. It will block most ranged attacks and abilities such as frostbite and whirlwind (whirlwind now requires line of sight). You can use it to trap, evade, buy time, and even do damage. The one who places it can interact with the firewall to pass through it.