You can't really have a Pathfinder game without monsters. Fighting monsters has been one of the central conceits of Dungeons & Dragons since the beginning and Pathfinder is no exception. Yet after a while, fighting the same monsters again and again can become dull. Kobolds and goblins can be great fun once in a while, but eventually people want something different. So it's not surprising that people are constantly thinking up new kinds of monsters to add to their games and surprise other players. And it's also not surprising that books of monsters can creep up to five volumes with probably more to come.
The Pathfinder Roleplaying Game Bestiary 5 adds over 300 more new monsters to the Pathfinder game. With every Bestiary volume containing in the vicinity of 300 monsters, that makes approximately 1500 monsters just from the Bestiaries (and not counting the numerous other sources that introduce monsters). In my review of Bestiary 4 a couple years ago, I pondered a bit on the thought of when does the number of monsters become too big. I suppose the only answer is either when people grow tired of them or when the new monsters stop being original and interesting. Bestiary 5 does not seem to be at either of those points, though I wonder how far off that point is.
In fact, I like Bestiary 5 a great deal. On an initial look-through before reading it more thoroughly, there were numerous monsters that drew my attention, that made me want to know more about them, and screamed to be included in one of my games sometime down the road. There's a wide variety of monsters present, with every type represented and the spread between them being fairly even. Ooze is a monster type that is often under-represented, but there are quite a few new oozes in this book. Along with that there are lots of magical beasts, constructs, undead, vermin, fey, and so on. In addition, there are several mythic monsters, and Bestiary 5 is the first hardcover book to contain monsters using the occult rules from Occult Adventures. The monsters cover a wide variety of challenge ratings as well, from 1/6 to 24. The bulk of the creatures are in the low- to mid-CR range, but there are also a sizeable number of high-CR monsters as well.
While the majority of the monsters are entirely new to this book, some are compiled from other sources. A few are monsters from earlier editions that have (perhaps surprisingly) not yet been updated to Pathfinder, such as brain moles and firbolgs. Others originally appeared in Pathfinder Adventure Path or Campaign Setting volumes, or various adventure modules. These include the akhat and guardian scroll (both of which originally appear in The Half-Dead City), along with others. For the most part, reprinting monsters like this doesn't bother me. Indeed, it can be a very useful thing. When monsters are scattered over numerous books that are not dedicated books of monsters, they can be hard to find. This puts them in one place (or just a few volumes). However, I do have an issue with the fact that several creatures in Bestiary 5 are reprinted from Inner Sea Bestiary. These include androids, ghorans, and all the robots from the earlier book. As Inner Sea Bestiary is already a dedicated monster book, it's not as difficult to find these monsters. Instead, their presence becomes redundant page space, and that bugs me a bit. It also dilutes the campaign setting somewhat.
That aside, there are still a lot of completely new monsters in Bestiary 5, many of them interesting and creative. The bone ship is a CR 18 creature that is literally an undead sailing ship, complete with bound souls that form its ghostly crew. There are quite a few other creepy undead in the book as well, such as the tiyanak (an undead infant or child) and the grim reaper (exactly what it sounds like). The manasaputras are a new class of outsider that reside on the Positive Energy Plane where they seek perfection and oneness with the universe. Sahkils are another new class of outsider. They are corrupted psychopomps. Tsukumogami are particularly fun outsiders that are amalgams of ordinary objects with kami. Numerous new fey dot the book, from hobkins and nunos (both kinds of gremlins) to the powerful glaistig, which is CR 21/MR 10. And there are the aforementioned oozes, including animate hair, doppeldreks (shapechanging oozes!), and living mirages.
As I mentioned above, Bestiary 5 is the first hardcover book to contain creatures using occult rules. Like in the softcover Occult Bestiary, many of these monsters have the psychic magic universal monster ability, and I still have the same issues with it that I outline in my review of that book (see the link). I really don't see the need to have spell-like abilities and psychic magic work in completely different ways. Unfortunately, this is a rules subsystem that is likely here to stay. Psychic creatures introduced in the book include the aforementioned manasaputras, psychementals (incorporeal beings formed from the collective unconscious of psychic beings), lotus trees (psychic plants), and esoteric dragons. These latter creatures are a new class of true dragons linked to the Esoteric Planes. They include astral, dream, etheric, nightmare, and occult dragons.
Bestiary 5 is, of course, full of artwork of the various creatures contained within its covers. The art varies somewhat in quality, and on the whole, I'd have to say it's not as good as the artwork in previous Bestiaries. Some of the monsters (like the occult dragon) just don't seem to come alive from the page. Most of the art is very good though (and I have to comment on just how cute the lotus leshy is).
Overall, Bestiary 5 is a good addition to my collection, and I'm sure I'll get quite a bit of use out of it. That said, the game is definitely creeping towards the point where the number of monsters will become too big. It will simply be overwhelming. I've made similar comments about feats, archetypes, etc. in other reviews, and I wonder just when the tipping point will be reached. I won't be at all surprised to see a Bestiary 6 eventually (though hopefully not for a couple more years), but I suspect anything more than that will reach the “too much” point for me personally. Regardless of that, however, I will certainly gain a lot of fun from Bestiary 5.