Pit Scorpion

A pit scorpion is a monster

In The Lightning Thief
In The Lightning Thief, (book 1), Luke summons Percy into the wods, and he expains his plot to take over Olympus, then he summons a pit scorpion, he tells Percy he shouldn`t go for his sword, the pit scorpion can kill in 60 seconds. When Luke is gone, Percy quickly goes for his sword and kills it, but he realizes it bit him and he passes out and wakes up in the Medical place.

Powers

 * It has a sting that can kill in a minute.
 * It can jump very far.