Portal Second Age is an odd one. A set full of very simple cards that would be pretty much forgotten these days if not for all the guns shown in the art. It didn't really have a storyline, but unlike the original Portal it did have a specific setting, the island of Caliman on the Southern hemisphere of Dominaria, a description of which was given in The Official Guide to Portal Second Age. A shorter version of that text ended up in the third volume of the Magic the Gathering Official Encyclopedia.
I can't say the setting is very deep though. One nation per color, conflicts along color wheel lines, that sort of stuff. The Alaborn somehow survived peacefully for "thousands of years" without contact with other cultures, but are now fighting the goblins and the swamp queen Tojira. The Talas merchants are getting into trouble by logging in the forest of the Norwood elves... you get the idea. The version from the Encyclopedia
has been re-posted here so you can read that if you're interested.
The most intriguing bits are the ones that tie it to the background of the Weatherlight Saga (Portal Second Age came out right between Rath block and Urza's block). Tojira lives in the ruins of a Thran city. That buzzsaw-weapon the ogres are using is powered by a Phyrexian mana battery. It is not outright stated in the text, but it seems the unusually high levels of technology (nightstalker engines, flying ships, all those guns) either originate from the Thran ruins or from more recent contact with the Phyrexians.
The longer version of the text from the Offical Guide hints at an even deeper connection to the Weatherlight Saga. It reveals that the Talas also use Thran tech, that the swamp dwellers trade "evil Phyrexian artifacts" with the goblins, and perhaps most telling in its vagueness: "the humans benefit from the genius of a great inventor." If that was just some random inventor among the Alaborn or Talas they surely would have been named right, like Tojira? But no, we just get that one enigmatic line. Which makes me wonder... are we actually looking at a proxy war between Urza and the Phyrexians here?
Unfortunately that's all there is. No further hints at what is going on, how the war might turn out or anything like that. With WotC's aversion to showing guns in their arts I highly doubt we will ever get an update. Even if we ever return to Caliman we will most likely find out it has been leveled during the Phyrexian Invasion or one of the subsequent Dominarian apocalypses, to explain how they lost all their guns. Though maybe we could salvage the
nightstalkers in a future Dominaria set? They are a unique Dominarian creature type and I always kinda liked their design. And hey, Dakmor itself is still around in a way, so...
All in all Caliman in a setting with a unique high-technology feel and cool hints about links to the larger continuity, but no really deep lore. In interesting blip on the Vorthos radar, but little more than that.
TIMELINE
There are a few timeline references in the text. Tojira came to occupy the swamp 10 years ago. The Talas started to chop down Norwood trees 30 years ago. The first skirmishes and disagreements between the nations started 150 years ago. Which of course raises the question: 150 years ago compared to what? I'm guessing the lack of a qualifier means the set takes place in the present, which was 4205 at the time of the Weatherlight Saga.
With there not being a real story for the set it's going to look a little weird on my timeline, but I guess I'll include it for completion's sake. All those backstory dates I'll save for now as not to clutter the timeline up any more than it already is, but I'll keep them in mind in case I ever make a timeline as detailed as the one of the Wiki.