This supplement introduces a new type pf nasty to the Pathfinder bestiary - seven different varieties of mosquitofolk, background, ecology, and lore (including defenses against them), and an adventure to subject your player characters to. The formatting is clean and well organized - the PDF is fully bookmarked and is in landscape format for easy viewing on screen. The artwork is somewhat simple and cartoonish, and the adventure map is very well done.

'There's no such thing as too many monsters' states the introduction, and when they come as well-presented as this one, it's hard to argue with that. Launching a series of monster books, this product looks at the mosquitofolk - who apparently would be quite nice if they didn't have this unquenchable thirst for blood. In the past, they had a burgeoning civilisation but this now lies in ruins as all they can think about is satisfying their addiction. It's not clear how they came to such a state, but it appears to be through the manipulations of their own leadership caste, the woundmages.

Reading on, we learn of their appearance and lifecycle, and the way in which their society is organised. Nowadays it is focussed solely on acquiring blood and controlling slaves - whose main purpose is to provide a blood supply rather than labour or other services. Even their language, once rich with poetry and literature, has degenerated to little more than communication on the capture of living targets.

Next come stat blocks on actual mosquitoes - giant ones, of course, and the feared swarm. One is a pest, but a whole swarm of them? These may be encountered as pets of the mosquitofolk or just as regular inhabitants of, well, the sort of places likes swamps and jungles in which you would expect to find mosquitoes. Finally, the dread mosquitofolk themselves appear. They are roughly humanoid in shape, but more like a giant upright mosquito with an insect head and wings, and that annoying buzz only louder. There's also the undead variant, the hollow, which is created deliberately by the woundmages from fallen mosquitofolk - cursed still with a desire for blood but unable to use what it collects. Most go mad. Being insects, there are also several varieties of mosquitofolk, specialised for different tasks, all honed to perfection to gather blood in their own way. Each, naturally, comes with its own special abilities and notes on their behaviour in combat.

Next comes encounter information - typical raiding parties you might be unlucky enough to meet in the jungle, as well as the gathered wisdom of how best to defend against them. Natives have developed several herbal concoctions, most of which work by making your blood unpalatable to the mosquitofolk. There's also a mini-adventure - set-up and encounter - which you can use when the characters stray into suitable territory in their travels. This includes a fully-detailed mosquitofolk lair, complete with map. Rather cleverly, three scenarios - depending on the level of the party - are provided, enabling you to pick the most suitable one when the opportunity arises. The book ends with an unlabelled player map of the lair and a world map.

This is an excellent example of how to present a new monster - replete with background detail that enables you to embed them into your campaign world, and with a detailed lair designed to accommodate adventure at several levels depending on the strength of the party you have at the time.