First, the relevant text:
Ring of the Void After you resolve your fourth or later non-Kiho action from Strategies in one phase: You may put his card into play from your hand.
Attack Phase; D. Fight battles; Subsection "Resolution Segment" [*]Once the last battle has ended, the Attack Phase ends. Battlefields cease to exist. Any units still at battlefields bow if they were attacking, and return home.
Next, the set up:
During the optional attack phase, if I play: [*]A strategy card called "A" and one called "B" during a combat segment at a province. [*]A strategy card called "C" and one called "D" during a different combat segment at a different province.
i.e. Four (or more) strategy cards, some of which were played at previous battlefields
Last, the question:
May I legally put The Ring of the Void into play after resolving card "D"? It's still the same attack phase since it hasn't ended because I've not resolved a battle at every province, correct?
I see no reason why I can't, I just never thought about it before and for some reason that made me skeptical.