Talos

Talos (Greek: Τάλως; Latin: Talus) or Tálon was a giant automaton made of bronze by the god Hephaestus,god of metalwoking in the Cretan tales incorporated into Greek mythology.

Mythology
He protected Europa in Crete, circling the island's shores three times daily while guarding it and throwing stones at any approaching ships to protect the island.

When the original Jason and the Argonauts approached the island of Crete for the Golden Fleece, Talos as the islands guardian, kept the Argo at bay by hurling great sized boulders at it. Medea, the sorceress, either drove him mad with drugs, or fooled him into believing that she could make him immortal by removing a nail and killed him with the same nail.

The Titan's Curse
Percy, Thalia, Grover, Zoë, and Bianca fought a malfunctioning prototype of Talos after Bianca stole an item from Hephaestus' junkyard. Since Hephaestus is very protective of his belongings (according to Aphrodite), even discarded ones, the automaton begins functioning when someone steals something from the junkyard. In this case, a small figure of Hades was stolen by Bianca for Nico, her brother as it was the only figure he didn't have. While fighting, the heroes find a hole at the bottom of the automaton's foot. Bianca enters the hole to try and make the machine malfunction, so that they could defeat him. He fell on some power lines and got electrocuted killing Bianca in the process.

Trivia

 * Talos is the only enemy Percy faces in the series that is not a monster, god, or demigod besides Festus.