Question

What did Percy notice about the new sword instructor, Quintus?
(Battle of the Labyrinth)

Answer 1

He seemed odd. he also found it strange on how he was seen around the entrance of the Labyrinth. I just read this

Answer 2

Percy noticed a strange mark on his shoulder i think. At first he thought it was a tattoo, but them realized that it was actually a brand. The mark was that of a bird, he was branded by the goddess Athena when he accidently killed his nephew.