Explorator – the melee and mobility path, this is intended to create a melee specialist that can move around between enemies and place strong single-target damage where needed. Additionally, since enemies moving out of melee reach triggers a free attack, they can be used to pin a ranged enemy down for at least one free hit as they try to back up. Some melee enemies also trigger opportunity attacks as they approach, allowing for the Explorator to sometimes act as a front-line tank to help logjam melee enemies to keep more fragile ranged characters behind him safe.
Secutor – the troop-leader path, the Secutor focuses on providing buffs for troops, either for more damage, more armour, getting them into the fight faster, or giving them free attacks. Sounds useful on paper, but in practice by the time the Secutor starts to get rolling, the other TechPriest classes have already left it in the dust.
Tech-Auxilium – a support class, with a scattering of abilities that don’t really reflect any central theme. Each of the abilities is useful for a different sort of build, making this a good class to dip into for other classes.
Lexmechanic – another support class, but this one with the very clear roll of CP generation. All 5 abilities are built around generating more CP, making this a must-have in most cases, particularly on some of the Ubjao missions where there is very little CP provided by archives.
EnginSeer – another support class, focused entirely on healing. Given that all damage that you haven’t repaired by the end of a mission costs Blackstone to repair (even if the amount is largely trivial), you’ll still want one of these for in-combat healing, if not necessarily to top everyone off as fights are wrapping up.
Dominus – the ranged weapon path, with a focus entirely on energy damage and effectively the opposite of the Explorator.
All skill paths upgrade in the same pattern of 9 ranks – odd ranks grant an ability (some are active with a cooldown or CP cost, others are passive benefits that are always on), while even ranks grant a piece of armour (head, torso, arms, or legs) in whichever order you desire. You can mix and match armour from multiple classes, but can only have one head, one torso, one arm, and one leg equipped at a given time (yes, make sure you equip them, they cost augment slots to use), making it important to consider which combination of kit you want for a TechPriest.