I recently purchased Terraria for my iPhone, and I'm getting along just fine; I've got experience from console and PC. When I was in the corruption farming rotten flesh, an orange message popped up stating:
50th Eater of Souls killed
The same thing then happened at 100. But this hasn't happened for any other mob that I've killed, I'm still very early on in the game so I've not seen many mobs yet.
I've looked around, and I found a Wiki entry describing how a banner is dropped after every 50 kills of a specific enemy. I must, however, assume that this feature isn't yet implemented in the mobile version of the game as no banner dropped.
So I'd like to know the purpose of this message, and if it really means anything at all.