Disclaimer: I was a backer on the Kickstarter for this project so I had rather high hopes for this product.
The Aventyr Bestiary states it is a 3.5 OGL and Pathfinder Compatible Product. It is a Pathfinder Product and OGL Compliant but it does not contain dual statistics.
One of the things I really like is that the Table of Contents is linked so you can click and go right to the creature. A+ for that.
The artwork is eyecatching though a tad cartoonish. That's just subjective opinion so if you love the artwork, I'm not going to burst your bubble.
Editing is less than stellar. That said, I'm still rather impressed with the variety of creatures.
I really wanted to like the Icons but Extraplanar is used far too often: It is listed as Climate/Environment AND Twice as Type/Subtype. For Climate/Environment, I would call it Planar so that there is less confusion. .For Type/Subtype, I think the second one was meant to be Outsider. It has the lighter blue circle. Air is also listed as an Environment and as Subtype. I much would have preferred Sky to Air for Environment. Sadly Marsh/Swamp has no icon. (Note the Half-Fiend Dryad may have that icon but it isn't listed). You have a few monsters that could use that. No icon is listed for Ruins/Dungeons for that matter.
What is the Fungus Type or is it a Subtype? There is an icon but no explanation and it is not in the PRD.
I noticed the Augmented Subtype was missing (this is important because I think it was needed for the Fleshdoll Rogue and is lacking though I will comment on that later). While there is an Evil Icon, there is no corresponding Good one. I don't know if this was done on purpose or just an oversight. You have Psionic as a Subtype in a few places but no corresponding Icon. Last of all, there is no Shapechanger icon.
Most of the creatures seem to comply with the standard rules, but I have neither the tiime nor inclination to crunch all the numbers. Suffice to say, unless something jumps out at me, I'm going to presume the stat blocks are correct.
Unique creatures aren't just Solitary. If there is only one of its kind, that should be noted (Exsangunator for example)
Now for the Nit Picks:
Creatures should not have Two Types unless one is an Augmented Type see Elemental Drake and Fleshdoll Rogue. Note: you need to list whch traits they keep and which they lose somewhere, because of conflicts. Immunities should still be listed individually not just as Construct and Undead traits as per Fleshdoll. DMs want the information at their fingertips and don't want to have to look that stuff up.
Creatures do "points of" damage not just a type of damage.
What gives with all the creatures that you couldn't be bothered to add an "s" to make plural. I find this to be just sheer laziness (not to mention it enables illiteracy).
The avatar of Alkumuoto doesn't have a plane of existance listed in Environment. Should an Evil aligned plane at least.
Why does the Biddlytree speak Druidic instead of Sylvan? Druidic is a secret language.
Chicken Coop is a Construct (and no mention of Baba Yaga even) but the Construction section is missing.
The Dark Angel is a wholly wasted Subtype in my not so humble opinion. You could have said this was an evil angel and or at least noted which special abilities are granted by the Subtype. "Subtypes add additional abilities and qualities to a creature." This new subtype is rather lackluster and lackng.
Elemental Drake has two Types. It looks like it should be the Dragon Type with Extraplanar and Native subtypes.
The Draaki has the Graldin Breath Weapon special ability that could have just been noted as Breath Weapon. The phrashing is confusing since it just seems to do fire damage.
Exsanguinator's Ecology section is missing.
Fleshdoll Rogue is all sorts of Confusing: Male Human Fleshdoll Rogue 5. Okay. But then how is it a Construct AND Undead as both are Types? Also, it doesn't need any of the Undead immunities since they are all covered under the Construct immunities. I'd like to see Construction section on this too.
On the other hand, the Forstdeath Dragon is a proper Undead. Sadly, these undead dragons lose their breath weapons entirely.
Fungiant is another favorite of mine. The trunk of a mushroom is properly called a "stipe." Yes, that is particularly nit picky.
Funglet is another Two Type creature. It looks like this is just an Intelligent Plant that happens to have a humanoid appearance. I'd just leave it as a Plant Type and lose the Humanoid Type. Plants are immune to all mind-affecting effects (charms, compulsions, morale effects, patterns, and phantasms). Immunity to paralysis, poison, polymorph, sleep effects, and stunning. What are those Subtypes (audire, funglet)? They should be noted somewhere or at least note some source where they can be found. You completely wasted an advertizing goldmine by not putting the book where this is in the OGL section. How do you think people find these books?
Gitwerc are a nice addition though it would have been nice to have dweorg too since the two are so closely related. And why isn't your book that has those listed in the copyright notice? This is exactly how people find your products because they are listed in your other books.
Goemul's deadspeech ability notes speak with dead, which as a spell should be in italics (really nit pickiing here).
Libreum is also spelled as Liberum. Which one is correct?
The grizzly bear rug is terrific and another one of my favorites as it can be used in many settings. I want this to be a magical beast however. A druid made it after all. Why is this as strong as normal grizzly bear since it is so much thinner? About 1/4 the weight of a male grizzly. Also, grizzly bears have a racial modifier to Swim, which is lacking but not noted so it appears to be a mistake. See here: http://paizo.com/pathfinderRPG/prd/bestiary/be-
Are gyeongsa warpstorms affected by natural or summoned weather?
I also am quite fond of the Ireful Hellion. A devil that is chaotic. It should retain its Lawful Subtype however even if its alignment is Chaotic. See Lawful Subtype.
I'm also fond of the Hordenheim riot. Thank you for acknowledging where you bend the rules.
Hoyrall warrior is another with two Types. Just because it is humanoid in shape doesn't make it Humanoid. This should just be an aberration.
Jinn Wizards are a bit of a misnomer since they aren't actual wizards at all and don't cast spells. They probably should have the Psionic Subtype since you have the icon for it.
Karz slug and Karz slug queen should also have Psionic subtype since you have an Icon for it. They may also have a Swamp Icon that isn't in the Icon list.
Should kra’tah have Underground icon since it isn't listed in their environments?
Mortdravva is not only Solitary but also seems to be Unique (see Organization).
If mutah can breathe air, then they should not have the Aquatic subtype. Just because a creature lives in an aquatic environment doesn't mean it has to have the Aquatic Subtype.
Naghith also seems to be Unique (See Organization)
Necro-pede's Psychic Vampire ability contains no game mechanics. How long does it take to feed and what happens to the victim it feeds off? Should there be a saving throw for example?
Nitnam also seems to be a Unique creature.
Nogth Ma’klurl’uth also appears to be a Unique creature. Madness Within ability has singular/plural issue. In the stat block the creature is an it (no gender is given) but in the flavor text the creature is noted as HE. Also, the drow witch is female. You should probably clarify this mystery.
Ollphéist should be Magical Beast not Animal as it has an Intelligence of 5.
I'm not sure why Petrous has the elemental subtype: Elementals do not need to breathe, eat or sleep. No elemental immunities are listed. The text contradicts the subtype.
Phoso are kinda slow for their size at 40 ft., even with that many legs.
Pubo should be magical beasts not animals as they are naturally psionic.
Rellum the correct subtype is extraplanar not outsider. Outsider is a Type. Environment should list its home plane.
Snow Roc's Icy Gust probably shouldn't be a free action as it is a supernatural attack. That means that a target can take damage from its Icy gust and from its normal attacks in the same round. It should be a standard action otherwise it seems overpowered.
Rufidier should probably have an "s" as a plural. Also, free actions should not be attacks. Flame gout should be a standard action.
Rust mite swarm is bound to piss off a lot of players. I see this as a Deus Ex Machina to get inappropriate items away from PCs.
I'm not sure I understand the purpose of the salt worm's regenerating maw. Why would it ever lose its maw in the first place? Methinks it needs to be rewritten for clarity. What wound is regenerating? See your other gaping maw ability in Szaboans,
Screaming Severed Skulls melee attack should read 1d2 plus 1 cold. Don't take shortcuts with + signs. I'm not sure why it has a slam attack instead of a bite since it has no limbs. Does it ram its skull into you?
Why should an incorporeal shadow rat be able to bite a corporeal foe, even if it's just to allow a bite that does only Strength damage? That's pretty harsh for a CR 1 encounter. It can immobilize a level one party in an hour. I see a TPK here.
Shield Wardens should have their home plane listed in Environment or at least any lawful plane. What a boon if the party can get this kind of help!
Sigbin have the potential to be a TPK as well. I assume Negative is negative energy damage in the damage. That doesn't see intuitive but I'm willing to let it pass. The party isn't likely to have any items that bypass negative energy damage so this is a bit tougher than would be expected.
Skildpadder(s) should probably be magical beasts rather than animals considering they're the offspring of bulettes.
Cold Mutated Ogre Spiders are a mouthful to say the least. Not a fan of the name.Does this imply that there are other ogre spiders that aren't cold or mutated?
Giant legwater spiders aren't all that swift as they only move 30 ft., which is standard for a medium sized creature. The walking on water thing is just gonna get it called Jesus Spiders. You know that right?
A sloth spider with a hasted burst. Oh, the irony.
That's some black pudding, just saying. I guess there is no real Stone Salve-Shaped Template; pity.
Riding slug? Ewww. Also death from above when it drops on you. How much do these weigh? See falling damage.
Tri-Tongue Horror source material isn't listed in Copyright section. At least you cite to it.
Do ethereal and incorporeal creatures have a diminished sense of smell? See Veinar.
Vestraadi subtype text is missing.
Waspite should do electricity damage not electric damage.
Zvucni (really isn't that pronounced zucchini?). It is NOT an ooze. It's an aberration.
Zwerc.Again with the double Types. It looks like it should be Fey (augmented humanoid, dwarf, zwerc). Again reference to dweorg.
[4 of 5 Stars!]