“Why sirens?,” I hear you ask. Well, because the Wyrd Sisters send Thalia off to stop a serial killer who’s murdering them in Wyrd Calling.
Sirens are not viewed positively. A lot of people, Thalia included, see them as nothing more than parasites. They’re often found in colonies around the base of cliffs and near bridges on large rivers. Sometimes, however, there just isn’t room or a young siren feels the need to go off and explore the wider world, and that leads to them heading into cities. It’s not such a bad thing when they’re in a colony, as they cause the suicides where people jump off the cliff or the bridge or wreck their boats on the jagged rocks. They can’t do that in the city, although they are usually to blame when someone drowns in the water obstacle on the golf course or that particularly crafty puddle.
The reason that they’re generally considered parasites is because they don’t have a positive place in the scheme of things. They kill people but they give nothing back. Fortunately, they only need to eat once every few years, but that leaves them with a lot of free time to be particularly entitled, lazy, obnoxious, arrogant, and all round unpleasant princess types.