Let's start with the easy stuff. In this 100 page PDF you get about 98~ pages of Call of Chthulhu support material. The art and graphics are ok, about what you would expect from RPG publishing of this level, and the layout is clean if a little cramped.
There is a good deal of British-centric material in this issue (which makes sense since the publishers are British) and I think it would be of good use to someone using Cubicle 7's Laundry RPG. Obviously the tone of this material is more serious than the base tone of the Laundry RPG, but since both use the underlying Call of Cthulhu mechanics, fitting one into the other wouldn't take a lot of effort on the part of a Keeper/Game Master.
My favorite part of the issue is the first article: Terra Occulta: An Atlas of Strange Places. I am a sucker for these sorts of articles because they can really help to fire up the imagination of a Keeper, in addition to providing some interesting (and exotic locales) for games. Each location write-up isn't long, it is more of a story hook than anything else, but they also have the benefit of not having any mechanics tied to them. This means that you can also use them in your GURPS Horror games, or even a globe-trotting game of Angel or Ghosts of Albion. These locations range from spots in Britain to Africa to Australia to South America. Either as a starting point for your horror games, or a bit of exotic and interesting flavor, this atlas should cause a lot of creative sparks for Keepers (or any horror game master for that matter). Terra Occulta is something that could be done up as an RPG supplement and I would buy the hell out of it, if it meant not having to do some of the research myself. It's like Wikipedia with its facts straight.
The next most useful article was actually two of them, both about the British Museum (and again something that could be useful for those playing the Laundry RPG, particularly Americans who may not know as much about the UK and places like the British Museum). My personal introduction to the British Museum was through RPGs: both the Call of Cthulhu boxed set that introduced me to that game and the first edition of GURPS Horror had maps to this wonderful and mysterious place. But, I always wondered....How do I use it in my games when I've never been there?
Well, David Conyers fills in some of those gaps with The British Museum: London's Centres of Knowledge, Part One. One weakness in this article is the fact that the "Part One" does mock me a bit. Knowing that behind the scenes difficulties have (long!) delayed the release of Black Seal #4 means that part two of this article has yet to be released. What arcane secrets does it hold?
That weakness in mind, this is still a strong article that (thankfully) does not have a cliffhanger ending. No "to be continued" haunts the resolution of the article or its quality. The URL for the Museum's web site is handy and provides some nice visuals to allow a potential Keeper to be able to describe the place, even with out having been there, with enough of a level of confidence suitable for gaming. Also, the section on the security is very handy since we all know that sooner or later some player group or another will attempt to break into the British Museum to steal something. Also good is the lack of game stats. Again, this is an article that can be used for a wide variety of games. Yes, there is an NPC writeup of a curator for Call of Cthulhu, but this doesn't take up much space in the article, and it does help give some guidance on what sort of NPCs the player characters could encounter. A new mythos tome also rounds out this article.
Once you have the basics of the location, the companion article: Rare and Unusual: Pararnormal Artefacts at the British Museum does give you some meat to hang off of the bones of the previous article. Again, the write-ups in this article are mostly generic (and each entry has an illustration as well) but there is material for both the BRP Call of Cthulhu and Call of Cthulhu d20. The mechanics are still minimal, mostly referencing spells and in the case of d20 material saving throws and ACs of objects. The article ends with three new spells, dual statted for BRP and d20, and a creature tied to one of the objects. Like with the locations in Terra Occulta, the beauty of these objects is how they can be used as a springboard for stories for Keepers. Need an occult artifact to keep out of the hands of the bad guys? There you go. The article even tells you it's location within the Museum for better mapping. Need an occult object to stop the bad guys? This article has that too.
Just on the strength of these two articles and all of the entry points that they can give to Keepers for their Call of Cthulhu games. Story hooks and springboards beyond the hackneyed "You inherit a musky old book from an uncle who died under mysterious circumstances" can do nothing but benefit your games.
On to a bit of bad. The weakest spot in this issue was the Cages comic. I have been a fan of comics longer than I have been a fan of RPGs, and this did nothing to draw me in. Perhaps it was because it was the third installment? I don't know. The art was passable, and it's strongest selling point may be the fact that it reminds me a lot of the art from Caliber Comics in the 90s (a favorite comic publisher of mine even today). Beyond that, the comic really didn't do anything for me, and the issue could have been stronger with even a couple of NPC write-ups in its place.
Also a strong article, but of little use for the games that I run is A Road Less Travelled: A Rough Guide To Fighting Evil In A Hot Country. This article provides a good deal of Call of Cthulhu/BRP mechanics for heat, deserts and survival. And for fans of such things, there are two pages of tables of diseases and sicknesses that one can come down with in inhospitable places. There are also some new animal write-ups for animals native to Africa. This article ties closely to the adventure The Spiralling. The Spiralling is designed for use with PICSES, the British counterpart to Delta Green. A well-written adventure, that could fairly easily be reskinned for someone not using Delta Green or PISCES, it just doesn't fit my needs. I'm not a pre-published adventure kind of game master.
Wood Ingham's False Mythologies sets up a European cult that has ties to the Mythos and Atlantis. I know that there are a lot of gamers tired of ties to Atlantis, but I think that when they are well done, it shouldn't matter if it's tied to a myth like Atlantis, or a more "popular" myth among gamers. This article is one that is well done, which should surprise those who are fans of Wood's work on the World of Darkness for White Wolf. The article is rounded out with new spells, NPC write-ups and notes for integrating the cult into both baseline Call of Cthulhu campaigns and Delta Green ones. Also, definitely worth the price of admission.
Mini-adventures, a write-up of the cult of a Tibetan god and a UN conspiracy set in Antarctica that ties into both Delta Green and Beyond The Mountains of Madness round out the issue. I do think that I found Resolution Zero to be a little too derivative of the Planetary story Island Zero (even without the giant monsters).
Over all, I found Black Seal #3 to be a well-written and well-designed supplement for Call of Cthulhu. The articles support a wide variety of Call of Cthulhu campaigns and styles, along with enough generic support that any horror game master would find something useful with it's virtual pages. It is definitely worth the money spent on it. Hopefully it will make enough that Black Seal #4 will come out and we will get part two of the article on the British Museum.