As the first paragraph suggests, this odyssey does not take place in Boston or the surrounding area. It starts at that other statue of a giant head on that other Massachusetts avenue – the one in Indianapolis. Starting from that statue, the traveler travelled southwest on Massachussetts Avenue, turning onto New York where Mass Ave ends, then turning south onto Meridian street. While proceeding south, the traveler climbed The Soldiers’ and Sailors’ Monument, then continued south on Meridian until Georgia Street. The traveler continued to travel west after passing Capitol Street. This places the traveler inside the Indianapolis Convention Center. On the weekend described, this situates the traveller’s odyssey as occurring during Gen Con. The rest of the description is Gen-Con specific, and most of the remaining travels take place in the exhibitors’ hall. (A map of this hall is available here: http://files.gencon.com/2015.ExhibHallMapwithLinks.pdf)
The construction work happening (without Norsemen is Cardhalla. Turning to the south after passing the up/down escalators in the east-west hallway described brings you into the exhibitor’s hall from the middle entrance on the north side. From here, there are seven distinct legs of travel. After the first six legs, the traveler asks a question, and a conversation results from that question which mentions an ordinal number. The first leg of travel brings the traveler to the Game Crafter booth (booth 737). Their booth has a large statue of a steampunk robot (their mascot) every year, and the answer to the question – what is the robot’s name? - is COG. The third letter (“third-party”) is G.
The second leg of travel brings the traveler to the Dr. Who North America booth (booth 132). The answer to the question – what kind of machine is that? – is a DALEK. The second letter is A.
The third leg of travel brings the traveler to the Warpo booth (2939), where you could get your picture taken with CTHULHU. (Now you all know what he’s been doing since last year’s Mystery hunt.) The seventh letter is U.
The fourth (very short) leg of travel takes the traveler to the booth of PERPLEXT (3032), whose game offerings consist entirely of games in stick-of-gum-sized packages. We do not, however, recommend actually trying to chew the cards in lieu of gum. The fifth letter of PERPLEXT is L.
The fifth leg of travel takes the traveler to the Z-MAN booth (2009), of which the first letter is Z. Z-Man is a well-respected games publisher that was included as a stop for the traveler primarily because a stop which provided a Z was required.
The sixth leg of travel takes the traveler to the Geek & Sundry booth (1509), where the thing everyone was excited about was TITANSGRAVE, of which the fifth letter is N.
The last leg of travel takes you to the Paizo booth, where the person you seem to recognize is Mike Selinker, perhaps best known to mystery hunters as a puzzle-writing member of The Evil Midnight Bombers What Bomb At Midnight. His book “The Maze of Games” (which, really, is what this puzzle was) was available for sale there. Putting the letters from each stop in the order he describes gives you the answer NAZGUL.