Soulbond ftw

109.5. The words “you” and “your” on an object refer to the object’s controller, its would-be controller (if a player is attempting to play, cast, or activate it), or its owner (if it has no controller). For a static ability, this is the current controller of the object it’s on. For an activated ability, this is the player who activated the ability. For a triggered ability, this is the controller of the object when the ability triggered, unless it’s a delayed triggered ability. To determine the controller of a delayed triggered ability, see rules 603.7d–f.

112.8. The controller of an activated ability on the stack is the player who activated it. The controller of a triggered ability on the stack (other than a delayed triggered ability) is the player who controlled the ability’s source when it triggered, or, if it had no controller, the player who owned the ability’s source when it triggered. To determine the controller of a delayed triggered ability, see rules 603.7d–f.

I still think that it works.

608.2c The controller of the spell or ability follows its instructions in the order written. However, replacement effects may modify these actions. In some cases, later text on the card may modify the meaning of earlier text (for example, “Destroy target creature. It can’t be regenerated” or “Counter target spell. If that spell is countered this way, put it on top of its owner’s library instead of into its owner’s graveyard.”) Don’t just apply effects step by step without thinking in these cases—read the whole text and apply the rules of English to the text.

I think that first you change control of creatures by reigns of power and then apply the flickering effect with returning to your (opps) battlefield.

I state that I generate a continous effect:

611.1. A continuous effect modifies characteristics of objects, modifies control of objects, or affects players or the rules of the game, for a fixed or indefinite period.
611.2. A continuous effect may be generated by the resolution of a spell or ability.
611.2c If a continuous effect generated by the resolution of a spell or ability modifies the characteristics or changes the controller of any objects, the set of objects it affects is determined when that continuous effect begins. After that point, the set won’t change. (Note that this works differently than a continuous effect from a static ability.) A continuous effect generated by the resolution of a spell or ability that doesn’t modify the characteristics or change the controller of any objects modifies the rules of the game, so it can affect objects that weren’t affected when that continuous effect began.

614.14. An object may have one ability printed on it that generates a replacement effect which causes one or more cards to be exiled, and another ability that refers either to “the exiled cards” or to cards “exiled with [this object].” These abilities are linked: the second refers only to cards in the exile zone that were put there as a direct result of the replacement event caused by the first. If another object gains a pair of linked abilities, the abilities will be similarly linked on that object. They can’t be linked to any other ability, regardless of what other abilities the object may currently have or may have had in the past. See rule 607, “Linked Abilities.”

In other words: Why does Phage/Endless Whispers works and this combo not? Who is the controller with respect to rule 109.5 and endless whisper?

Information about an object that’s no longer in the
zone it’s expected to be in, or information about a player that’s no longer in
the game. This information captures that object’s last existence in that zone
or that player’s last existence in the game. See rules 112.7a, 608.2b, 608.2g,
and 800.4g.


Phage is still in the same zone and both players are still in the game.  There is no need to look at LKI.
 
Phage returns to play under your control, due to the following 3 rules which were already posted, with the relevant parts highlight


112.7a Once activated or triggered, an ability exists on the
stack independently of its source. Destruction or removal of the source after
that time won’t affect the ability. Note that some abilities cause a source to
do something (for example, “Prodigal Pyromancer deals 1 damage to target
creature or player”) rather than the ability doing anything directly. In these
cases, any activated or triggered ability that references information about the
source because the effect needs to be divided checks that information when the
ability is put onto the stack. Otherwise, it will check that information when
it resolves. In both instances, if the source is no longer in the zone it’s
expected to be in at that time, its last known information is used. The source
can still perform the action even though it no longer exists.


112.8. The controller of an activated ability on the stack is
the player who activated it. The controller of a triggered ability on the stack
(other than a delayed triggered ability) is the player who controlled the
ability’s source when it triggered, or, if it had no controller, the player who
owned the ability’s source when it triggered. To determine the controller of a
delayed triggered ability, see rules 603.7d–f.
109.5. The words “you” and “your” on an object
refer to the object’s controller, its would-be controller (if a player is
attempting to play, cast, or activate it), or its owner (if it has no
controller). For a static ability, this is the current controller of the object
it’s on. For an activated ability, this is the player who activated the
ability. For a triggered ability, this is the controller of the object when the
ability triggered, unless it’s a delayed triggered ability. To determine the
controller of a delayed triggered ability, see rules 603.7d–f.



The combination of these three rules basically say "you activated the ability, therefore you are the controller of the ability, the "your" on the ability was set to you as the controller when it was activated, and since it is no longer tied to the source of the ability, it doesn't matter where the source goes
 
ddd