Create your opening repertoire by picking up lines you like from the Pirc, Modern, Philidor, Old Indian, King Indian, Hippopotamus, Rat Defense (while having more possibilities to avoid the lines you don't trust) It is too early to characterize this repertoire or the kind of players using it. Usually supporters of 1..d6 appreciate:
-little provocations (as shown by players like Bent Larsen, Anthony Miles, Tigran Petrosian, Julian Hodgson, Michael Basman, Rainer Schlenker, Stefan Bücker, Baadur Jobava and Jules Welling -to have "The space DISadvantage", appreciate Reti's theory about controlling versus occupying space, prefer the counterattack above blunt attacks and gambits -are not afraid for an early exchange of queens also giving up the right to castle after 1.d4 d6 2.c4 e5 3.dxe dxe4.QxQ KxQ and 1.e4 d6 2.d4 Nf6 3.Nc3 e5 (starting off as a Pirc or 1.e4 e5 2.Nf3 d6 3.d4 Nf6 in the Philidor sequence) 4.dxe5 dxe5 5.Qxd8+ Kxd8.

===

Some sources:
(1)"Play 1…d6 Against Everything: A Compact and Ready-to-use Black Repertoire for Club Players", New in Chess, 2017, 208 pages by Erik Zude and Jörg Hickl

(2)"A Cunning Chess Opening for Black: Lure Your Opponent into the Philidor Swamp!", New in Chess, 2015, 288 pages by Sergey Kasparov

(3) "The Old Indian: Move by Move", Everyman, 2015, 496 pages by Junior Tay

(4) "1...d6: Move by Move", Everyman, 2012, 400 pages by Cyrus Lakdawala

(5) "The New Old Indian: A Repertoire for Black Against 1 d4", 2011, 160 pages by Alexander Cherniaev and Eduard Prokuronov

(6) "The Philidor Files: Detailed Coverage of a Dynamic Opening", Everyman Chess, 2007, 304 pages by Christian Bauer

(7) "A Universal Weapon 1.d4 d6: The All-Purpose Defence for Black", Chess Stars, 2011, 224 pages by Vladimir Barsky

(8) "Geheimwaffe Philidor", Chessgate, 2005, 132 pages by Christian Seel

(9) "An Explosive Chess Opening Repertoire for Black", Gambit, 2002, 192 pages by Jouni Yrjola and Jussi Tella

===

Content/ The Umbrella Themes for the games

1) Endgame Variation
-1a)The d4-Endgame Variation
-1b)The e4-Endgame Variation

2) Philidor

3) Pirc

4) Modern (Setups after 1.e4. Hedgehog, Hippopotamus etc.)

5) The Old Indian

6) The Wade Defence (Also called Hodgson or Tartakower Defence, with The Pribyl/Rat)

Appendix

I The pros of Space Advantage

II The contras of Space Advantage