Advance
Mestnichestvo
The Mestnichestvo is an ancient system that assigns positions of state to people based on the antiquity of their lineage and the seniority they hold within their families. The most tangible demonstration of this system involved the seating order of Boyars at the Tsar's table, which reflects their individual rank and precedence.
Advance tree
The game files don’t say where this goes: it has no requires, so the game places it in the 
Discovery tree itself.