Percy was a gargoyle, but not a very good one.

Most gargoyles sit on castles, watching all the people below.  Some of them warn you if you’re in danger.  Some of them spit giant goobers on your head.  But all of them have one thing in common: they live high above the ground with no trouble at all.

But not Percy.  Percy was scared of heights.

No, not just scared.  Percy was terrified of heights.  He had nightmares about climbing stairs.