FimFiction Link - Short ID: 122/the-thessalonica-legacy
Published: Jul '11
Coming in at 70,000 words across 19 chapters, The Thessalonica Legacy is a 2011 Human-in-Equestria crossover fic with the mecha-infused neo-feudalism of the BattleTech/MechWarrior universe, and despite its age is a shining example of how to tackle this genre. Writing for an already niche setting during the nadir of its popularity, the writer has gone to great lengths to smoothly introduce a reader unfamiliar with BattleTech to the setting, whilst also putting his impressive knowledge of BattleTech's nuances on full display for those already in the know, even going as far as to mimic the style of official BattleTech novels, complete with the traditional jargon glossary in the unlikely event that the reader gets tripped up somewhere.
Meanwhile on the pony side, Thessalonica holds up just as strong. While somewhat hindered by their Season 1 characterizations, Twilight and friends ring true, and the tone of Equestria is very fitting with the early seasons, with content that wouldn't suit the show only ever injected by the humans. A collision between idyllic Equestria and a much more violent universe is one of the oldest tropes in crossover fiction, but few manage to pull it off with the grace Thessalonica does. It even avoids the traditional pitfall of the ponies becoming ancillary to the story, complimenting the traditional "humans have to get home" plot with a parallel mystery for Twilight to unravel, tying into curious lore implications within the show itself.
All in all, wither you're reading for fun or to learn how it's done, The Thessalonica Legacy is one of those oldfics that stands the test of time, and is most certainly worthy of yours.