Why do you think banishing the top 4 of your deck changes in any meaningful way the distribution of your deck?
Say your deck is 25% lands. That means, on average, one of the four cards Impulsive Wish banishes is a land. This does not change the land distribution of your library in any way.
People run fetchlands to thin their deck because they fetch LANDS. Meaning there are fewer lands for you to draw in the future. Your card, since it is completely random, does not change the distribution of lands or anything else in your deck in any way.
If I ran no other wishes, why in the world would I want to run this card over even the lowly Thought Scour? Why would I just make resources disappear? Those milled cards are a resource for any number of things (as has been discussed in this thread without you ever addressing it). Why would I instead want to remove those resources from the game, indeed play a card SPECIFICALLY to remove cards in my deck from the game and make them harder to access?
If I was going to banish random cards just to wish for them, why not just draw them directly from my deck like a normal person?
I cast this spell, and I get a random card from my deck. How is this any different than a spell that just says "draw a card?" Seems unnecessarily complex for what is basically drawing a card.
Enforcer 3 (Prevent the first 3 combat damage that would be dealt to this creature each turn. When damage is prevented this way, this creature deals that much damage to another target creature.)
I mean, it's still a broken ability, but at least it works (I think).
Deck of Many Things 5
Artifact
1, T: Choose one at random that hasn't been chosen before.
* Draw three cards.
* Take another turn after this one.
* You gain 100 life.
* Discard two cards.
* An opponent creates a 5/5 black Demon creature token with flying.
* You lose the game.
Token Nephilim WUBRG
Legendary Creature - Shapeshifter
Tokens you control count as nontokens.
TAP: Create a 1/1 Shapeshifter creature token with changeling.
Changeling
6/6
While this looks like it works when you check under the hood it falls apart. With abilities that are constantly checking a status meaning they are "as long as X, Y" Y much come after X in layers. This unfortunately means you can't check p/t to grant anything since p/t is the last layer. Any abilities that checks p/t can't be static so it locks in the time its checking.
This is interesting and I've never come across it before (because they don't print cards that don't work, obviously) but it makes sense. With this rule you can't have stuff like "This creature gets +1/+1 as long as its power is greater than its base power" or other questionable stuff like that. I'll have to keep this in mind designing cards in the future.
Things can't happen in the middle of spells resolving. When Primal Surge resolves, all the creatures are on the battlefield, and only then can their ETB abilities go on the stack. Regal Force will "see" all your other green creatures.
Apex Predator 1GG
Creature — Elemental
Hexproof from planeswalkers
As long as Apex Predator's power or toughness is greater than 3, it has indestructible.
3/3
No. The first thing that happens at the beginning of your upkeep is Ephemerate goes on the stack. You can activate Mangara in response, but it will be exiled before Ephemerate resolves.
EDIT: Technically the Rebound trigger goes on the stack, but there is no way to resolve it so Ephemerate resolves first.
If you look at a 4th Ed Mana Vault it looks like it has an activated ability that can only be activated during the upkeep. However, that's no longer what the card says. The current Oracle Text of Mana Vault says that it only has one activated ability, the mana ability.
This is much better than any of the Crusaders because it can block arbitrarily many creatures. Against red and black decks this guy can just turtle up and never let any attackers through and never be able to be spot removed. That's a huge problem for limited in particular.
Say your deck is 25% lands. That means, on average, one of the four cards Impulsive Wish banishes is a land. This does not change the land distribution of your library in any way.
People run fetchlands to thin their deck because they fetch LANDS. Meaning there are fewer lands for you to draw in the future. Your card, since it is completely random, does not change the distribution of lands or anything else in your deck in any way.
If I ran no other wishes, why in the world would I want to run this card over even the lowly Thought Scour? Why would I just make resources disappear? Those milled cards are a resource for any number of things (as has been discussed in this thread without you ever addressing it). Why would I instead want to remove those resources from the game, indeed play a card SPECIFICALLY to remove cards in my deck from the game and make them harder to access?
If I was going to banish random cards just to wish for them, why not just draw them directly from my deck like a normal person?
You can't go infinite with it like you're saying. You get the token at the beginning of the next end step.
I mean, it's still a broken ability, but at least it works (I think).
Deck of Many Things 5
Artifact
1, T: Choose one at random that hasn't been chosen before.
* Draw three cards.
* Take another turn after this one.
* You gain 100 life.
* Discard two cards.
* An opponent creates a 5/5 black Demon creature token with flying.
* You lose the game.
Legendary Creature - Shapeshifter
Tokens you control count as nontokens.
TAP: Create a 1/1 Shapeshifter creature token with changeling.
Changeling
6/6
This is interesting and I've never come across it before (because they don't print cards that don't work, obviously) but it makes sense. With this rule you can't have stuff like "This creature gets +1/+1 as long as its power is greater than its base power" or other questionable stuff like that. I'll have to keep this in mind designing cards in the future.
Apex Predator 1GG
Creature — Elemental
Hexproof from planeswalkers
As long as Apex Predator's power or toughness is greater than 3, it has indestructible.
3/3
EDIT: Technically the Rebound trigger goes on the stack, but there is no way to resolve it so Ephemerate resolves first.