Solace hired you for one specific skill — surgery, linguistics, locksmithing, demolitions, accounting, performance. Cartography is the job; your specialty is what makes you indispensable when the cartography goes wrong. You're not really a Path-walker by nature. You're a [whatever] who happens to walk Paths now. Your colleagues are field assets; you are sometimes also a field asset, but mostly you are the only person on the team who can do the thing.
▌ Tier modifier
Player choice — +1 to any one domain, −1 to any one other. Pick the domain your specialty most depends on. The +1 may push a Proficient domain to Expert — the Specialist is one of the three Backgrounds permitted to start at Expert tier. Doing so invokes the Cost of Expertise. The −1 should reflect what your specialization cost you — the medic who never learned to fight, the linguist who can't bluff, the accountant who falls apart under physical pressure.
Choose your specialty. A one-sentence concept that defines what you do better than anyone else on the team. Examples: combat medic, forensic accountant, lock and security specialist, classical linguist, demolitions engineer, stage performer, pathologist, bookkeeper. Work with your GM to make it specific.
▌ Perk · Tradecraft
Within your specialty, you operate at a level above your tier. In any roll the GM judges to fall within your declared specialty, you treat your Effective Tier as +1. This stacks with other modifiers within the ±2 cap. The specialty must be narrow enough to be specific.