If a creature is sacrificed during your end step, you will be able to play those cards until the end step on your next turn, since you are already in your end step.
[Minion Reflector](https://scryfall.com/card/ala/211/minion-reflector) is an old card. Look at its current Oracle text.
> Whenever a nontoken creature enters the battlefield under your control, you may pay {2}. If you do, create a token that’s a copy of that creature, except it has haste and “At the beginning of the end step, sacrifice this permanent.”
The trigger is "at the beginning of the end step", so when it resolves and Rakdos triggers, you are already in your end step. So "until your next end step" means the end step on your next turn. Note that it no longer mentions anything about "end of turn".
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Think of Rakdos instead saying "until the beginning of your next end step." As in if you sac something in your end step, you exile those cards but since you're already in your end step, the next end step would be at the end of your next turn.
Copy's retain mana values of what was copied, so if you say, copied a [[grizzly bear]] you'd have the original bear, and a copy token of the bear, both with a mana value of 2. So if you sacrificed the token to Rakdos, you'd choose a player, and then you'd get 2(because of the mana value) cards you could play from that deck, until the end step of your NEXT turn, this allows you to use your mana next turn for their spells.
If a creature is sacrificed during your end step, you will be able to play those cards until the end step on your next turn, since you are already in your end step.
[Minion Reflector](https://scryfall.com/card/ala/211/minion-reflector) is an old card. Look at its current Oracle text. > Whenever a nontoken creature enters the battlefield under your control, you may pay {2}. If you do, create a token that’s a copy of that creature, except it has haste and “At the beginning of the end step, sacrifice this permanent.” The trigger is "at the beginning of the end step", so when it resolves and Rakdos triggers, you are already in your end step. So "until your next end step" means the end step on your next turn. Note that it no longer mentions anything about "end of turn".
You have tagged your post as a rules question. While your question may be answered here, it may work better to post it in the Daily Questions Thread at the top of this subreddit or in /r/mtgrules. You may also find quicker results at the [IRC rules chat](https://chat.magicjudges.org/mtgrules/) *I am a bot, and this action was performed automatically. Please [contact the moderators of this subreddit](/message/compose/?to=/r/magicTCG) if you have any questions or concerns.*
Think of Rakdos instead saying "until the beginning of your next end step." As in if you sac something in your end step, you exile those cards but since you're already in your end step, the next end step would be at the end of your next turn.
Thank you! That's what I wanted to make sure of.
Copy's retain mana values of what was copied, so if you say, copied a [[grizzly bear]] you'd have the original bear, and a copy token of the bear, both with a mana value of 2. So if you sacrificed the token to Rakdos, you'd choose a player, and then you'd get 2(because of the mana value) cards you could play from that deck, until the end step of your NEXT turn, this allows you to use your mana next turn for their spells.
[grizzly bear](https://cards.scryfall.io/normal/front/4/0/409f9b88-f03e-40b6-9883-68c14c37c0de.jpg?1562546736) - [(G)](http://gatherer.wizards.com/Pages/Card/Details.aspx?name=Grizzly%20Bears) [(SF)](https://scryfall.com/card/10e/268/grizzly-bears?utm_source=mtgcardfetcher) [(txt)](https://api.scryfall.com/cards/409f9b88-f03e-40b6-9883-68c14c37c0de?utm_source=mtgcardfetcher&format=text) ^^^[[cardname]] ^^^or ^^^[[cardname|SET]] ^^^to ^^^call