I don't know what those are. [Although he has recently met a dragon!] Titans are humanoid creatures that can vary greatly in size, anywhere from 3 meters to 15 meters tall, but I'd say around 8 is the norm. They're completely mindless beasts, incapable of communication or even animalistic empathy... Their only goal in existing is eating humans.

This in itself wouldn't be problematic if it weren't for their incomprehensible numbers and near-invincible regenerative capabilities. Cannon shot can only slow a Titan, even if their heads are blown off. The way they are killed, what I was trained in, is very specific and very dangerous. And so, humanity's recovery is very slow.