Designing Magic's Cards

In the process to make magic's cards there are basically two ways to start: top-down or bottom-up. In the first case the theme takes priority. In the second case the mechanics take priority. An example of top-down:

Suppose that I have an idea of a card that is about wind. Destructive wind gusts. In the context of Magic that means a card that affects creatures, probably some card that destroys or deals damage to one or more creatures. Due to color restrictions, with each color having access to certain effects, the card can't be of any color. Let's see some of cards that were made:

All of them are sorceries, being temporary events. They are all green, because in Magic green is the color of nature and that hates creatures that fly. All of them depict a destructive wind force, tornadoes or hurricanes. All are named accordingly and the art matches the idea of hating creatures that fly. In Magic every world that is visited has a story and depending of the story natural catastrophes may be part of that world's story. If those catastrophes are really important and there is room for cards to depict them, one or more cards are made to represent those events. The specific details about how much damage or whether or not it's going to also hit players is a decision about the card's mechanics. What came first was the idea of a hurricane or tornado. How strong that card is going to be is a different matter that deals with the intended power level for that card.

Addendum: I don't know if the mentioned cards were made top-down or bottom-up. I took them as examples.

The other way around is bottom-up, first what the card does, then the theme. For example, suppose that I want to make cards that has the goal of destroying creatures on the battlefield. There are many ways to destroy a creature. For example:

From left to right, the first card is black. Black is the only color in Magic that can destroy creatures without any restrictions. The card's name references an assassination. Does it have any relationship with discarding a card? Depends on how you see it. The card's intention could have been to convey fear and death at the same time. I don't know because I don't know what the person that made the card was thinking. The second card is white and white is associated with spells that can only destroy creatures with some condition, such as the one that card has. The card's name is about revenge and it fits with the card's restriction of targets. Other similar ideas could be firing at the back, a trap, beheading, punishment, a divine bolt. And the card could have different conditions to destroy the creature such as the creature is attacking, it dealt damage to another creature, it destroyed another creature, etc. It all depends on what flavour they want with that card. If the card is going to called an arrow, sword or lightning bolt and whether the art is going to depict an arrow, sword or lightning bolt, it's a creative decision that comes on a later stage. The last card is an artefact with no color and artefacts can destroy creatures, albeit with a much higher mana cost. The card's name and the black mana fit the idea an altar where sacrifices are made. That altar may or may not be part of that world's plot.

Overall, each set in Magic repeats the same basic mechanics. There is always destruction of creatures, destruction of artefacts, creatures that deal damage, creatures with high power and toughness. However, there isn't enough room for everything and some mechanics have more room than others. Some sets are going to have more of some mechanics and less of others. It all depends on many factors such as the public's acceptance, aiming at faster or slower gameplay, aiming at more or less destruction, etc.

Addendum: I don't know if those cards were made with bottom-up. I used them to give an example.

In level design we can apply the same idea used in Magic. Begin with the theme or the mechanics? Going back to the castle. Let's say that we have a castle is being used an operational base by some corporation in the middle of a war. What style is the castle going to have? German? British? Japanese? What kind of corporation is using the castle? Are they terrorists? Is it a religious group? Is it an industry that produces food? What are they doing in that castle? Are there machinery making weapons? Is radioactive waste being stored there? Are scientific experiments taking place there? The better the descriptions are and with a clearer and well defined atmosphere it becomes easier to develop the level.

Now the other way around, mechanics first. Let's say that the player is going to swim and has arrows and a bow. Let's think about a flooded place that the player is going to traverse. The player can swim underwater for up to 30 seconds before having to come up for air. Let's think about tunnels and spots to breath. Then some levers that open up underwater doors. Suppose that there is a platform that functions as a lift, however it can't stay up because it goes down with its own weight. The player is required to shot an arrow tied to some metal piece to jam the gears that move the lift. During this whole time we weren't thinking on the theme or location, not directly at least. We were focused on the obstacles. So were are the obstacles in? A submarine? It can be. A flooded castle? It can be. A ruined temple under a lake? It can be. We left the theme and atmosphere to be decided on a later stage.