Trivia Contest

Visit — An opponent chooses red card, sorcery card, or legendary card, then mills a card. You have ten seconds to name something from the chosen category that starts with the same letter as the milled card. If you do, claim the prize!
Prize — You get {TK}{TK}{TK}, then you may put a sticker on a nonland permanent you own. Sacrifice Trivia Contest and open an Attraction.

Unfinity

Visit — An opponent chooses white card, land card, or planeswalker card, then mills a card. You have ten seconds to name something from the chosen category that starts with the same letter as the milled card. If you do, claim the prize!
Prize — You get {TK}{TK}{TK}, then you may put a sticker on a nonland permanent you own. Sacrifice Trivia Contest and open an Attraction.

Visit — An opponent chooses blue card, enchantment card, or creature type, then mills a card. You have ten seconds to name something from the chosen category that starts with the same letter as the milled card. If you do, claim the prize!
Prize — You get {TK}{TK}{TK}, then you may put a sticker on a nonland permanent you own. Sacrifice Trivia Contest and open an Attraction.

Visit — An opponent chooses black card, artifact card, or expansion, then mills a card. You have ten seconds to name something from the chosen category that starts with the same letter as the milled card. If you do, claim the prize!
Prize — You get {TK}{TK}{TK}, then you may put a sticker on a nonland permanent you own. Sacrifice Trivia Contest and open an Attraction.

Visit — An opponent chooses green card, instant card, or named mechanic, then mills a card. You have ten seconds to name something from the chosen category that starts with the same letter as the milled card. If you do, claim the prize!
Prize — You get {TK}{TK}{TK}, then you may put a sticker on a nonland permanent you own. Sacrifice Trivia Contest and open an Attraction.

If you’re choosing a card name, every name that starts with a letter starts with the same letter as itself. If the milled card fits the chosen category, you can just choose that name.

The official card database at Gatherer.Wizards.com is available to settle disputes if players can’t agree if the named card fits the chosen category.

The ten seconds starts once the card is milled. Someone should be ready to start a timer or start counting down from ten.

You can only name actual Magic cards from products that have been released. Things that have been previewed but not released yet don’t count.

You can’t look up cards online before naming something, even if you’re fast enough to do it within ten seconds. That would be impressive. But also cheating.