Monstrology is new to Wizard101. Basically this is allowing players to extract animus from creatures you battle, right now you can extract from: undead, wyrm, parrot and polar bear. To extract animus you would need to add one of these cards to a spell card and hit the enemy to extract animus. You only need to hit the enemy once to extract. Hitting the enemy multiple times will not extract more.
Your level of Monstrology does matter. If you're just beginning you won't be able to extract from let's say rattlebones ex, he is level 14. You can gain levels faster by using the triple animus elixir. for only 150 crowns you can use this elixir for an hour. Rattlebones Ex extract is 1 point with the elixir 3. I'm not sure if this changes as my level goes up. I'm hoping it does. ;)