22 Jun 2015
If you cast a card “without paying its mana cost,” you can’t pay any alternative costs. You can pay additional costs such as kicker costs. If the card has mandatory additional costs, you must pay those.
22 Jun 2015
Check to see if there are two or more instant and/or sorcery cards in your graveyard as the spell resolves to determine whether the spell mastery ability applies. The spell itself won’t count because it’s still on the stack as you make this check.
22 Jun 2015
If the card has {X} in its mana cost, you must choose 0 as its value.
22 Jun 2015
If you can’t cast any instant or sorcery cards (perhaps because there are no legal targets available) or if you choose not to cast one, then Talent of the Telepath finishes resolving. Any of the revealed cards you didn’t cast will be put into that player’s graveyard.
22 Jun 2015
If the spell mastery ability applies, you’ll cast the two cards in order. The one you cast last will be the one that resolves first.
22 Jun 2015
You cast the instant and/or sorcery card(s) from your opponent’s library as Talent of the Telepath is resolving. Ignore timing restrictions based on the card’s type. Other timing restrictions, such as “Cast [this card] only during combat,” must be followed.
22 Jun 2015
The cards will be put into their owner’s graveyard after they resolve, not yours.