I played against a gentleman today (we both had Orzhov decks with Extort creatures) who, after playing a creature with Extort, claimed that if you had mana left over you could pay its Extort cost without having to play a spell to trigger the Extort.
I know that sounds wordy, so I'll put it like this:
Turn 3, he had no creatures on the field. He played Basilica Screecher and after paying two mana to put it on the field, Extorted me once. (By his reasoning, the creature was a spell and thus he could Extort me)
I'm pretty sure that he was wrong (the text says "When you play a spell", which, presumably, means anything other than the creature with Extort), but it opens up a whole bunch of questions for me - when a creature with Extort hits the field, does the ability enter the field at the same time as the creature or do they come in at slightly different times? Can Extort work like a Kicker cost?
From the moment it hits the field it can start to trigger extort, but it has to be on the field for extort to trigger. Since it is not on the field when you cast it extort will not trigger from that card (unless something else already on the field has it).
edit: to clarify extort is a normal triggered ability that triggers when you cast a spell, which means that it triggers and goes on top of the spell and thus will always resolve before the spell that triggered it. If the extort ability is not there when you cast a spell it doesn't trigger and it can't look into the past to see that you cast a spell once it hits the field.
On the subject of erroneously "you may [perform an action]" and performing that action multiple times, a good way to explain it is to ask yourself whether or not you want to perform that action first. If yes, then you perform that action. In this case, you pay either W or B, and then determine that you've performed the action, but then you can't perform that action again because the effect doesn't allow you to.
It's a good way to explain to others how a "you may [perform an action]" effect works and why you're not allowed to perform that action multiple times unless it explicitly specifies that you can (this is why multikicker and kicker are different abilities).
Private Mod Note
Rollback Post to RevisionRollBack
How to use card tags (please use them for everybody's sanity)
[c]Lightning Bolt[/c] -> Lightning Bolt
[c=Lightning Bolt]Apple Pie[/c] -> Apple Pie
Vowels-Only Format Minimum deck size: 60 Maximum number of identical cards: 4 Ban list: Cards whose English names begin with a consonant, Unglued and Unhinged cards, cards involving ante, Ancestral Recall