Been trying to use some dark world monsters in a fiend deck, and i've been finding that twin twister and back to square one are not working with dark world monsters such as Sillva, Lucent, and Broww, so I'm assuming it's bugged.

its not a bug, the discard on both card are for cost, dark world have to be discarded by card effect to trigger

How does one determine whether or not there's a "cost"? Is it because of the whole "discard, THEN do such and such"? And not only that, but even if there was a cost, how does a cost prevent the effects from activating, since you're still technically discarding them? It just doesn't make sense to me as the spells initially say to discard a card before doing something.

The Dark World field spell still works, despite having a cost, if I'm reading it correctly. "Discard 1 Fiend-Type monster, then draw a card."

How does one determine whether or not there's a "cost"? Is it because of the whole "discard, THEN do such and such"? And not only that, but even if there was a cost, how does a cost prevent the effects from activating, since you're still technically discarding them? It just doesn't make sense to me as the spells initially say to discard a card before doing something.

The Dark World field spell still works, despite having a cost, if I'm reading it correctly. "Discard 1 Fiend-Type monster, then draw a card."

No, you aren't reading it correctly. The Dark World field spell says this: "Once per turn: you can banish 1 Fiend-type monster from your graveyard; discard 1 Fiend-type monster, then draw 1 card."

The cost is banishing a Fiend-type monster from your graveyard. Usually costs are followed by ";", then the effect happens.

Costs are NOT the same as effects. Costs are what activate the effect. There IS a difference. Like mentioned before, Dark World only activate when being discarded by a card effect (not a cost).

There is plenty of material about how Dark Worlds work. Hope you like reading.

All the Dark World Rulings 

Costs 

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Hmm... thanks for clearing things up, it never struck me that the banishing part of the dark world field spell was the cost. I thought it was sort of a two-step sort of cost, but that second part was actually just a result of the first. Although, regardless I still do think such rulings are horrifically ambiguous, especially when they physically use the word discard.

Hmm... thanks for clearing things up, it never struck me that the banishing part of the dark world field spell was the cost. I thought it was sort of a two-step sort of cost, but that second part was actually just a result of the first. Although, regardless I still do think such rulings are horrifically ambiguous, especially when they physically use the word discard.

It's easier than it seems. Just look for the semi-colon in a sentence in the card's effect, treat everything before it as the cost, and everything after it as the effect.

For older cards that haven't received their text update, more often than not the word "to" separates the cost from the effect, with the cost appearing before the "to".

One of the links I gave you will tell you every card that works with Dark Worlds (pretty sure).

It is just a matter of practice, and getting to know the game more.

Yes, Yugioh does have very very confusing text sometimes. Personally, I think they should color code certain parts of their effects to help make it easier. (Red = cost ect)

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What about the card "Back to Square One"? Does this card still count as a cost? It reads "Discard 1 card from your hand. Return 1 monster on the field to the top of the owner's deck." Normally with costs, the effect happens as a result of discarding, but back to square one only states to "Discard. Return.", rather than "Discard THEN Return".

That is most definitely a cost. Discarding is a requirement for activation.

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