DDR 

Isn't that a similar case to "whenever you cast" vs ETB? I have that with my Sea Monsters deck when my Kiora, Sovereign of the Deep is on the field and do cast one of my big monsters. Her effect basically gives me a better Cascade whenever I cast a Sea Monster creature from my hand, letting me look at as many cards from the top of my Library as the Monster's Mana Value and then cast a spell with equal of less MV. This resolves while the Sea Monster spell is still on the stack and before it enters the battlefield. The second spell then would also trigger "whenever you cast" effects, if their other conditions are met. It should be similar with Nadu, as his effect also contains "whenever." Meaning that his effect will still resolve normally before he turns into an Elk without it, making all other creatures under his controller's, well, control lose the ability as well.

Someone’s already replied but are you talking about Oko targeting Nadu, or what’s left over after Oko targets Nadu’s fellow creature? Assuming 2. Oko’s elk ability and Nadu ability to give an ability are both continuous effects in layer 6. So it comes down to time stamps. If Nadu was already on the field, then a Nadu trigger resolves and you are left with an elk with no abilities. If we have an elk and then Nadu is cast, whats left is an Elk with Nadu’s text stapled on to it. If it’s number 1. Oko’s ability targets Nadu and goes on the stack. Nadu’s ability triggers and it goes on the stack. Resolve Nadu’s card reveal trigger first and then turn him into a vanilla Elk. This is me trying to apply knowledge learn from this videos. I wouldn’t take it as gospel.

What's the scenario and question? If you're wondering if Oko's ability triggers Nadu's ability the answer is yes. If Amy has a Nadu and Grizzly Bear and Nick Oko's the Grizzly Bear Amy will get one trigger. Then Grizzly Bear will become an Elk with no abilities. It has no abilities because Nadu's about granting continuous effect has an earlier timestamp than Oko's ability taking away continuous effect. 613.8 says two continuous effects with no dependency on each other are applied in timestamp order.

​@TheParallaxian in all cases, Nadu will become a 3/3 elk with no abilities, and no other creatures will have the ability from Nadu. Nadu's controller would get to draw a target off the Oko ability targeting if it is the first or second time this has happened in a turn.

@@TheParallaxian Since you now have 2 continuous effects applying on the same layer, we will check for a dependency. Since Oko's ability will affect how and what Nadu's ability will apply to, we will apply that first. Now that we've applied Oko's "lose all abilities" to Nadu, Nadu no longer has abilities to apply to itself or others.

When applied to nonland cards, play and cast are synonymous

Ironically, I believe this is the major reason why this change in wording was introduced. Previously, the word "play" was used to refer to activating an ability, casting a spell, and playing a land. This was confusing because the rules for all these things are wildly different, so they started using different words to describe these different actions.

As marowakcity implies, "play" lets you play land while "cast" does not.

That's just because it's a Time Spiral card; if they reprinted it today it would say cast

When a vehicle is crewed and the ability resolves, the P/T printed on the vehicle is treated as its base P/T (CR 301.7b). If *Clone* copies a crewed vehicle, the Clone will also have that P/T. Although the *Phyrexian Metamorph* only has P/T when it is crewed, any effects that modify P/T of it will still function, but only once it becomes a creature later (CR 208.3); so, regardless of if the vehicle copied was crewed or uncrewed, the following ruling will still apply. The effect from *The Master, Transcendent* sets the metamorph's P/T in the P/T layer, and because that applies after the copy layer, the 3/3 set will override whatever the vehicle's printed P/T is. e.g. Phyrexian Metamorph enters as a copy of a crewed Consulate Dreadnought (7/14). Its P/T is 3/3.

From gatherer: Panglacial Wurm's ability works only while you're searching your own library. The effect that caused you to search needs to say "search" and "library," and you need to be looking through your own library for this to work.

I believe you can because they are able to cast the Wurm and you control them. After casting the Wurm they would control it

i beleive its because mutation says to counter "up to" one spell - you can choose to counter no spells and not need a target, so the copy wont fizzle

Yeah, this works in paper Magic as well. For spells with a variable number of targets, if that value is 0 (say, "up to 1 target spell"), then no targets were declared for that instance. In this circumstance, **Repulsive Mutation** has one and only one target: the creature. This triggers Ivy, of course, and it functions because a copied spell retains ALL choices and targets made in the original (CR 707.10) barring any exception in how the spell is copied. Ivy becomes the target and the copy resolves because no target spell was ever given. CR 707.10e only applies for spells with many targets, but Repulsive Mutation only had one.

Actually no! Escape is an alternate casting cost, while Unearth is an activated ability.

No, it is casting cost

It's already been answered, but to provide the specific rule (and feed the algorithm): 702.138a Escape represents a static ability that functions while the card with escape is in a player’s graveyard. “Escape [cost]” means “You may cast this card from your graveyard by paying [cost] rather than paying its mana cost.” Casting a spell using its escape ability follows the rules for paying alternative costs in rules 601.2b and 601.2f-h.