The Agate Companion is a brief description of a new figurine of wondrous power, whose purpose is to curse an animal companion with the primal power of wrath, giving it both significant power and making it harder to control. Animal companions often get short shrift in detailed magic items, so it's great to see them get some attention. The designer's notes at the end add a personal touch and give some ideas for other primal powers to affect animal companions with. Another interesting aspect of the figurine is that its curse is difficult to break - although a remove curse spell will work, a specific condition must be fulfilled in order to do so. This is a good chance for a GM to set out a quest or challenge, though there is also a list of possible curse-removal conditions at the end. I particularly appreciate the high-level skill checks supported by this product, revealing more and more secrets about the history and purpose of the item.
The PDF has no bookmarks, but the length is such that this isn't necessary. Due to the texture in the background the pages, it might be difficult to print out legibly. Nevertheless this is a decent product, well worth a look if you're a d20 fan.