The Taris Purple Mastery Datacron is located in the Republic Resettlement Zone map on Taris grants Mastery +2 (it used to grant Willpower + 2 before the stats changed).
The closest Republic quick travel point is the Aurek quick travel point and the closest taxi is the Waypoint Station Aurek Speeder speeder point, both in the middle of the map.
The Taris Purple datacron is in the Hospital Basement and is only available to Republic characters (Imperial players must make a Republic character to unlock this datacron). Finding this datacron will give you a permanent stat boost of Mastery +2 to all your characters on your server, and will unlock the Galactic History 26: Naga Sadow’s Deceptions codex.
Taris Mastery +2 Datacron (Republic)
Taxi: Waypoint Station Aurek Speeder
Location: Republic Resettlement Zone - Hospital Basement
Codex: Galactic History 26: Naga Sadow’s Deceptions
How to Get the Taris Purple Mastery Datacron
You can see this purple Datacron through a slit in a pipe while exploring the Sinking City map, but you’ll need to find a different way to get to it through the Hospital.
Quick Travel / Taxi
Run to the Hospital
Run north east along the path to the hospital – you’ll wind up at the main entrance on the ground floor
Heroic Fallen Stars republic is very close
Go Through the Back Entrance
Go to the back of the hospital and enter through back door into the basement
Find the hidden path behind a pile of crates
Head deep into the hospital’s basement, and look for a pile of crates concealing a door on the bottom floor of the basement.
Jump over the crates, and follow the secret tunnel path until you reach the datacron!