#kitodemonsoul

[magicjudge]

I have Phenax,God if Deception on my field.I tap another creature to activate the effect it got by Phenax. My opponent then destroys said creature with Doomblade,does he still have to put cards from his library in his graveyard or not? Best regards

Yes.

Once an ability has been activated, that ability exists on the stack independent of its source.

In this particular case, the game will use the creature’s last known toughness to determine how many cards will be milled.

[magicjudge]

Is a creature with shroud still affected by abilities like deathtouch?

Yes.

Shroud only stops effects that specifically target the creature. If the card doesn’t use the word “target” in the effect, then shroud doesn’t stop it. Shroud doesn’t stop untargeted effects like deathtouch or Languish or Wrath of God.

[magicjudge]

Can I use Duskmantle Guildmages first ability multiple times to stack it? For example I activate it twice and 4 cards enter my opponents graveyard this turn,does he lose 4 or 8 life?

Yes, the delayed trigger set up by each instance of the activation of Duskmantle Guildmage will trigger separately for each card. 

Your opponent will lose 8 life.

[magicjudge]

Does sacrificing multiple creatures/cards (for example by Archfiend of Depravities effect) happen all at once or one after another?

All the creatures are sacrificed simultaneously and will all see each other die.