Everything Else — Riftbound Rules

Players control their own Champion Legend. When a player Plays, Hides, or Creates a Card or other Game Object, they are established as that Game Object's Controller.

Section 191 — 21 rules

191.1.
Players control their own Champion Legend.
191.2.
When a player Plays, Hides, or Creates a Card or other Game Object, they are established as that Game Object's Controller.
191.3.
For Spells, they are the Spell's Controller.
191.3.a.
That player chooses targets.
191.3.b.
That player chooses modes.
191.3.c.
That player pays costs.
191.4.
For Permanents and Runes, when they Enter the Board, that player is assigned as that Game Object's Controller.
191.4.a.
That player may make decisions about the Game Object's Inherent Abilities.
191.4.b.
That player may make decisions about the Game Object's Unique Abilities.
191.4.c.
That player may make decisions about any game effects or decisions necessary while the card is being played.
191.4.d.
That player may make decisions about any game effects created from "When you play me" effects of Permanents.
191.5.
For Abilities, they are the Ability’s Controller.
191.5.a.
By default, the Controller of an Ability’s Source is the Controller of that Ability.
191.5.a.1.
If an Ability’s Source is located in a non-Board Zone, the Ability’s Controller is the Owner of the Source.
191.5.a.2.
If an Ability allows players other than the Controller or Owner of its Source to play it, the player that plays the Ability Controls the Ability.
191.5.b.
Changes to Control of an Ability’s Source do not change Control of that Ability.
191.5.c.
That player chooses targets.
191.5.d.
That player chooses modes.
191.5.e.
That player pays costs.
192.
When a game effect or rules text refers to the Controller of a specific object, it can be referring to either context interchangeably.
192.1.
The method of assignment of control is different, but the status of Control is the same across all Game Objects.