Sorin Markov

Controlling a player doesn’t allow you to look at that player’s sideboard. If an effect instructs that player to choose a card from outside the game, you can’t have that player choose any card.

While controlling another player, you can see all cards in the game that player can see. This includes cards in that player’s hand, face-down cards that player controls, and any cards in that player’s library the player may look at.

In a Two-Headed Giant game, Sorin’s second ability causes the targeted opponent’s team’s life total to become 10. Only the targeted player is actually considered to have actually gained or lost life.

You can’t make any illegal decisions or illegal choices — you can’t do anything that player couldn’t do. You can’t make choices or decisions for that player that aren’t called for by the game rules or by any cards, permanents, spells, abilities, and so on. If an effect causes another player to make decisions that the affected player would normally make (such as Master Warcraft does), that effect takes precedence. (In other words, if the affected player wouldn’t make a decision, you wouldn’t make that decision on their behalf.) You also can’t make any choices or decisions for the player that would be called for by the tournament rules (such as whether to take an intentional draw or whether to call a judge).

If the player affected by Sorin’s third ability skips their next turn, the ability will wait. You’ll control the next turn the affected player actually takes.

You can’t make the affected player concede. That player may choose to concede at any time, even while you’re controlling their turn.