Sorin Markov, Rakdos, Lord of Riots

[Jlamb5]

 If I play {Sorin Markov} and use his second ability, does this count as a loss of life allowing me to cast {Rakdos, Lord of Riots} and then allowing each creature to cost 1 less to cast?

[Iandtormentor]

Any decrease in life is loss of life.

[Hays413]

If I play {Sorin Markov} and use his second ability, does this count as a loss of life allowing me to cast {Rakdos, Lord of Riots} and then allowing each creature to cost 1 less to cast?

For a player's life total to become 10, what actually happens is that the player gains or loses the appropriate amount of life. For example, if the targeted opponent's life total is 4 when this ability resolves, it will cause that player to gain 6 life; alternately, if the targeted player's life total is 17 when this ability resolves, it will cause that player to lose 7 life. Other cards that interact with life gain or life loss will interact with this effect accordingly.

Taken from gatherer.

So using this, whatever life lost to get players life total to ten is; that's how much less creatures are to cast.
Alternatively, if the players life total is less than 10, it will have no Interaction with the Lord

RESOLVED

[Keyeto]

Well, beat me to the punch, guys. I've got a ruling for you, to back it up!

118.5. If an effect sets a player's life total to a specific number, the player gains or loses the necessary amount of life to end up with the new total.