Animorphs - a play-by-post rpg

As you and a group of your friends are walking home you take a shortcut through a construction sight. Suddenly a ship comes from out if the sky and crashes. You go to check on whoever it ia in the ship and you see a blue horselike alien with a scorpian tail and stalks on the end of his eyes. He tells you your world is in danger. Parasitic Alien Slugs are taking ovet people to slowly take over the entire earth. As he lays there dying he gives you a cube and tells you to lay a hand flat on it and it will give you the ability to morph.