28 cards where the illustration contains “theros-faction-sy...”

Aerial Formation (Journey into Nyx #30)
Ajani's Presence (Journey into Nyx #2)
Chariot of Victory (Journey into Nyx #159)
Chosen by Heliod (Theros #5)
Commanding Presence (Theros Beyond Death #7)
Commune with the Gods (Theros #155)
Decorated Griffin (Theros #7)
Defend the Hearth (Theros #156)
Evangel of Heliod (Theros #11)
Glare of Heresy (Theros #15)
Guardians of Meletis (Theros #217)
Hold at Bay (Born of the Gods #18)
Karametra's Acolyte (Theros #160)
Kynaios and Tiro of Meletis (Commander 2016 #36)
Kytheon's Tactics (Magic Origins #25)
Launch the Fleet (Journey into Nyx #15)
Ornitharch (Born of the Gods #23)
Phalanx Tactics (Theros Beyond Death #31)
Setessan Oathsworn (Born of the Gods #138)
Setessan Petitioner (Theros Beyond Death #199)
Setessan Training (Theros Beyond Death #201)
Soldier (Theros Tokens #3)
Soldier (League Tokens 2013 #4)
Starlit Mantle (Theros Beyond Death #67)
Supply-Line Cranes (Journey into Nyx #28)
War Oracle (Magic Origins #41)
Warriors' Lesson (Theros #184)
Winged Boots (Media Inserts #58)

The message was clear to Sorin—time to search for something else.