Copies that ability
When something allows a permanent to copy an ability, this is usually the same as "gains that ability." The differences are: there must be a card that has the ability that the ability is being copied from, and any quantifiers on that ability are the same as the card being copied from.
For instance, if you cast Prototyping and choose "wither" on a creature card that is prototyped, then the enchanted creature gains wither.
If you cast Prototyping and choose "bushido" on a creature card that is prototyped, if that creature had "bushido 2", then the enchanted creature gains bushido 2.
This ability provides a template for annihilator, bushido, protection, landwalk, and rampage to interact with prototype.
A note: "Protection from instants and from sorceries", for example, is a single protection ability.
(Another note: By rulings on the Cairn Wanderer, a card that says "as long as a creature in the graveyard has protection, this card has protection" automatically gets each protection as that kind of protection, so my new "copies" isn't necessary for those two keywords, but it still seems useful for the numbered abilities.)
"Drops <Name Grist> worth <X>" means the following: "When this creature enters the battlefield, choose an opponent. That player puts an artifact token named <Name Grist> onto the battlefield with 'Sacrifice <Name Grist>: Add <X> to your mana pool. You may use this ability only any time you could cast a sorcery."
"Killed it" is defined as follows:
When a creature dies, the controller of the most recent thing to affect it is considered to have killed it. Examples:
Prankster's Gambit is a new kind of counter that players can gain and lose. Any time a player has 10 or more Prankster's Gambit counters, they win the game as a state-based action.
Prototype N is a new keyword. Sometimes the N will be 0 and so not given- those cards will just read "Prototype."
Prototype N means: Look at the top N cards of your library. You may put one in your graveyard. Put the rest on the bottom of your library in any order. Then you may exile another target creature or artifact you control or target artifact or creature card in your graveyard with a prototype counter on it.
If N is 0, you just skip to "You may exile target...".
If something only happens "if you do" prototype, it refers to the second "you may" clause- specifically, whether you exiled something. It does not care whether or not you put something in your graveyard.
It's "another target creature or artifact" so you don't prototype something to its own ETB effect.
An example: I cast Skaian Meteor. I destroy target land, then I prototype 2. I look at the top two cards of my library. I can choose to put one in my graveyard. This doesn't need to be an artifact or creature card, but obviously if it is it gives me more options for prototyping. Then I exile either a creature or artifact I control, or a creature or artifact card from my graveyard, and put a prototype counter on it. All that counter does is mark that the card is "prototyped". Finally, because I did prototype something, I deal 2 damage to the controller of the land I destroyed. Had I chosen not to prototype something, no damage would be dealt.
Another example: I cast Amethyst Trypnid. It has "prototype" with no number. I may exile a creature or artifact I control, or a creature or artifact card in my graveyard, with a prototype counter. Afterwards, so long as there is at least one prototyped card I own, so long as at some point I have prototyped something, he has haste. It doesn't have to be something this card in specific prototyped.
A third example: I cast Unprototyped Kernelsprite. It puts a Kernelsprite creature token onto the battlefield which does, indeed, start out unprototyped, but has an activated ability that lets you prototype something with it. Each time you use that ability, you exile something (there is no number so you do not get to look at cards in your library first), and then the Kernelsprite token gains copies of all the activated abilities on each card you prototype with it, and the colors of those cards. Each Kernelsprite token tracks its own prototypes. However, they are all prototyped cards you own for purposes of cards like the Rust Imp or Queen's Ring.
A card is "prototyped" if it is exiled with a prototype counter on it.
A creature with vulnerability to something takes double damage from sources that they are vulnerable to.
Added Consort, Dersite, Felt, Guardian, Harlequin, Kernelsprite, Mayor, Monarch, Pastry, Player, Pony, Prospitian, Underling as new creature types.
Added Juju as a new artifact subtype.
An effect which 'interacts with' a library is any effect that targets that library, searches it, reveals a card from it, moves a card into it, or moves any number of cards from it into any other zone. While it would prevent an effect that puts a card into your hand, it does not prevent an effect that causes you to draw.
Insane Corkscrew Haymaker
Insane Corkscrew Haymaker sets up a delayed triggered ability that fires if the creature damaged by Insane Corkscrew Haymaker's effect dies at any point later that turn.
Remember that any time a modal spell is copied, it copies the chosen mode. As such if you use the cast Ironic Indulgence to prevent
a creature from attacking, and use its Guardian Rubric to copy the spell, the copy must also prevent a creature from attacking.
In the case of Ironic Indulgence, one option is never useful if the other is, so this won't really come up much.
The ability granted by Royal Command to use an activated ability is an exception to the Split Second restriction on using abilities.
See above for the definition of "killed it". Note that the game loss is a triggered ability that can be responded to, and if Snowman's controller loses the game before it resolves it will be removed from the stack.
Essentially, Windswept Questant lets you play with the top card of your library revealed only to you. Knowing what that card is becomes part of the information you have access to, just like you can look at the cards in your hand. You may look at the top card of your library whenever you want, even if you don't have priority. This action doesn't use the stack.
If the top card of your library changes during the process of casting a spell or activating an ability, you can't look at the new top card until the process of casting the spell or activating the ability ends (all targets are chosen, all costs are paid, and so on).