This card can play either side of Shift cards if the "past side" (front) is Darkness, regardless if the "future side' (front) is Darkness. This card cannot play Shift cards where only the future side is Darkness, as cards are always past side in the main deck.
Ex: "Interdimensional Monarch, Gill Lapis" can be played as itself or as "Space-Time Pursuer, Gill Lapis" with this card.
Ex: Neither "Alice of Light" nor "Alice of Shadow" can be played with this card.
This card only gains counters from cards that are put into a graveyard from the field because of the word "controls."