Just the summary of all the mobs that we could see so far =) Some of them only appear briefly in the trailer, but nevertheless it's interesting to know =) If you have some additional infos, go ahead. - Slimes - Slimes come in many different colours and sizes. They range from green over blue to grey, and the biggest slime yet seen is the mother slime. They move by hopping around, which makes it hard to predict when they're going to hit you, so you'll need a little bit of skill to hit them at the right time. They spawn underground and on the surface, but only at day. They drop gels which you can use to make torches. - Zombies - Zombies only spawn during night, and you'll only find them at the surface. If they find your house, they'll start knocking at the door, but they're not able to break it down. Only when there's a blood moon they get more aggressive and are actually able to break into your home. - Skeletons - You can find these creatures underground. They drop hooks which can be used to craft a grapling hook when you combine them with a chain which consists of 3 metal bars. - Demon Eye - These are little floating eye balls that come out at night. They start chasing you, and if they hit a surface or get hit by a weapon, they fly back in a short curve, than come back. - Eater of Souls - This floating creatures can only be found on corrupted area. Like the eye balls they chase you, but as far as I've seen it, they are a little bit slower. Also, it seems they become more and more if you've slain some of them. They drop meat chunks, which you can craft into something in combination with other items, with that you can summon the boss monster "Eater of Worlds". - Giant Worm - These hideous things can be found underground. They "dig" through dirt and even stone as far as I've seen it, but without actually destroying it. They jump from surface to surface, and you can hear them before they break out of the ground. It's possible that they follow you over a very long distance when you angered them once. - Hornet - They are exclusive to the underground jungle, and so far they were only seen in the Terraria trailer. They have a purple body, a yellow tail and they fly of course. - Man Eater - These giant plants were also seen in the trailer. Their head is attached to a long vine to reach out for the player to grab him towards itself. - Fire Imp - Also, they can be seen in the trailer. As far as I've seen, they look like little demons. They appear only in the hell-like parts of the underground. Also, they are able to shoot fireballs. - Bone Serpent - Some alpha tester said, that these are the most annoying, non-boss monster in the whole game. Like the giant worm they rise off the surface, lava in this case, and then dive back in. They seem to be pretty tough. - Devourer - One of them is seen for a veeery brief moment in the trailer. Basically, they are bigger and tougher versions of the giant worms. - Meteor Head - They are similar to the demon eye, except that they look like small, flaming meteors. I think they're special ability could be, that they are nearly invulnerable to physical damage, and can only be threatened by magic. - Goblin Warrior / Goblin Thief - Again, just from the trailer. I guess they only appear as a special event since, Red and Blue didn't encounter them yet in their LP.