This Pdf is 5 pages long. 1 page Cover, 1 page OGL, 1 page editorial, 2 pages creature, including AE-stats.

The creature features a well-crafted lore-section, designer's notes and a wonderful artwork: Being kinda cute and disturbing at the same time, it captures the potential of the Ur-Kasti Deta perfectly. The monster itself is not much of a combatant (although it's hard enough to kill!) and primarily intended as a "Plot-creature".
It succeeds at its role perfectly.
Especially due to the fact, that the Ur-Kasti Deta actually may be benign to some and not (like I thought after the other reviews) inherently evil.

The question of unwanted pregnancies and helping of barren parents have risen in my games more than once and may conjure interesting moral decisions. I agree with the other 2 reviews in so much, as it takes both mature players and a mature DM for this monster to work. If it does, be it as a villainous creature or a benign entity or something in-between or both, it is almost guaranteed to result in some memorable sessions.

For me as a fan of Ravenloft and similar dark settings, it is plain awesome.

I'd give it 5 Stars, but unfortunately, there is no advanced, second creature (like e.g. in "Hero's Bastard") and not as much fluff-text as in "Hero's Bastard". The prose that is there, is top quality, though.

Conclusion: This creature is gold for mature campaigns and works well as both villain and ally and can spawn a multitude of potential adventures.
What if the Ur-Kasti Deta had a hidden agenda, frenetically and subtly exchanging children according to some greater plan? Dun-Dun-Duuuunh!

Two questions remain, though: Will there be more "Monsters of Taboo" and will this be converted to PFRPG?

This creature has plenty of potental for interesting stories, the only reason why I don't give it 5 stars is because I see it more as a plot device than a monster as basically it wasn't meant to fight you as much as to pose a conundrum to be solved by indirect means.

Also, clearly this monster is adult material, not intended to be used by neither juvenile nor antagonistic GMs that would only use it for impregnating PCs left and right without a saving throw or playing Catch-22 with the party's paladin.

The Ur-kasti Deta or Taken of the Unborn is by itself an interesting concept with many role playing possibilities... of course the scenarios that come to my mind are darker than the light hearted commentaries of the designer.

I see dark quests and adventure hooks that can be used both for a horror or a very dark campaign where the heroes have either to protect an unborn child or recover it.

The Ur-kasti Deta are not by itself tough... but their abilities make them difficult to stop, so it can be pretty frustrating for players to confront them.

It also may seem arbitrary by the DM to get the PCs pregnant... even more if its a male character... but how to use this creatures is the province of every distinct DM.

I see a very concrete, complicate encounter, but it can be a lot more. a CE version of this monster can easily be agent of darker powers: The Unseelie courts as they exchange fae with mortal children, or they can be en Golarion servants of Lamashtu, delivering monstrous children into human or elven mothers, and their children into monstrous cultures.

That is about the creature, the format is clear, the layout is pretty good and the image is quite evocative, it brings to mind a short story of Horacio Quiroga, "the Feathered Pillow (el almohadon emplumado)" from "Stories of Love, Madness, and Death (Cuentos de Amor, de Locura y de Muerte)".