@tamerblur
TLD;DR: spam-Fireball aim sucks, this guy just used portal aimbot.
That's actually very clever. Assuming this dome is a recursive hemisphere where you teleport from one side to the opposite side, what about the vertical side? It seems that the fireballs exit at the same latitude, but at an inverted longitude (if you were to use Earth's coordinate system as a guide, with the Northern hemisphere's coordinates to coincide with the teleportation dome). In other words, shooting the exact top-center makes the fireball go directly back out the top-center (in which case the fireball will collide with itself and explode mid-air at the dome). On the other hand, aiming slightly aside from the top-center will have a parabolic effect where everything ends up redirecting to the EXACT CENTER OF THE DOME. What is at the exact center of this dome? The orcs.
Now, what is the downside of the spam-fireball attack? Accuracy. What does the dome do? Accuracy hack all projectiles to the center. FREAKING COMBO KILL, DAMN.
I might need to check through satellite dishes redirecting rays, but this should have the exact same effect (with the exception that the rays teleport their "longitude" after colliding with the side, but otherwise the same parabola-and-vertex-focus effect should be the same with the fireball trajectories.