#turn-based actions

This is a friendly periodic reminder that reminder text isn’t rules text. In the case of Sagas, I bring this up in order to point out that “after your draw step” is a lot shorter to write out than “at the beginning of your precombat main phase” and so it was used to save space on the cards.

Sagas get lore counters at the beginning of your precombat main phase, not in your draw step, so they have no interaction with cards that cause you to skip your draw step. (And they do have interaction with cards that cause you to skip your precombat main phase.)

It depends on when you make Mirage Mirror into a copy of the Saga. 

If you copy it in your main phase or later, then nothing much will happen and Mirage Mirror will just go back to normal when the turn ends. 

If you copy the Saga before your first main phase, then it will get a lore counter when your main phase begins and the appropriate chapter ability will trigger. If that happens to be the final chapter ability of the card it’s copying, then you’ll sacrifice it once that trigger resolves.

Whenever a step or phase begins, any turn-based actions for that step or phase happen first. e.g. you draw a card in your draw step. After these turn-based actions happen, any triggered abilities that trigger at the beginning of that step or phase will trigger. These triggers will then go on the stack before players receive priority. (Unless it’s the untap step, where no one ever gets priority, or the cleanup step where no one gets priority unless something triggers from the cleanup actions.)

So for Teferi’s Puzzlebox, you’ll first draw normally for your turn and then Puzzle Box’s trigger will go on the stack and resolve.

The easiest way I can think of to explain it is that innate game actions always come first in a step or phase: You draw a card before anything else in your draw step. You declare attackers before anything else in your declare attackers step. etc. Teferi’s Puzzle Box DOES trigger at the beginning of your draw step, but that doesn’t happen until after the mandatory game actions have happened.

I think you’re conflating turn-based actions, which are events that happen automatically on each turn, and state-based actions which are how the game deals with things like lethally damaged creatures and the like.

The turn based actions are as follows (as described in rule 703.4):

703.4a. Immediately after the untap step begins, all phased-in permanents with phasing that the active player controls phase out, and all phased-out permanents that the active player controlled when they phased out phase in. This all happens simultaneously. See rule 502.1.

703.4b. Immediately after the phasing action has been completed during the untap step, the active player determines which permanents he or she controls will untap. Then he or she untaps them all simultaneously. See rule 502.2.

703.4c. Immediately after the draw step begins, the active player draws a card. See rule 504.1.

703.4d. In an Archenemy game (see rule 904), immediately after the archenemy's precombat main phase begins, that player sets the top card of his or her scheme deck in motion. See rule 701.22.

703.4e. Immediately after the beginning of combat step begins, if the game being played is a multiplayer game in which the active player’s opponents don’t all automatically become defending players, the active player chooses one of his or her opponents. That player becomes the defending player. See rule 507.1.

703.4f. Immediately after the declare attackers step begins, the active player declares attackers. See rule 508.1.

703.4g. Immediately after the declare blockers step begins, the defending player declares blockers. See rule 509.1.

703.4h. Immediately after blockers have been declared during the declare blockers step, for each attacking creature that’s become blocked by multiple creatures, the active player announces the damage assignment order among the blocking creatures. See rule 509.2.

703.4i. Immediately after the active player has announced damage assignment orders (if necessary) during the declare blockers step, for each creature that’s blocking multiple creatures, the defending player announces the damage assignment order among the attacking creatures. See rule 509.3.

703.4j. Immediately after the combat damage step begins, each player in APNAP order announces how each attacking or blocking creature he or she controls assigns its combat damage. See rule 510.1.

703.4k. Immediately after combat damage has been assigned during the combat damage step, all combat damage is dealt simultaneously. See rule 510.2.

703.4m. Immediately after the cleanup step begins, if the active player’s hand contains more cards than his or her maximum hand size (normally seven), he or she discards enough cards to reduce his or her hand size to that number. See rule 514.1.

703.4n. Immediately after the active player has discarded cards (if necessary) during the cleanup step, all damage is removed from permanents and all “until end of turn” and “this turn” effects end. These actions happen simultaneously. See rule 514.2.

703.4p. When each step or phase ends, any unused mana left in a player’s mana pool empties. See rule 500.4.

State-based actions are checked before each time a player would receive priority. The state-based actions, as described in rule 704.5, are as follows:

704.5a. If a player has 0 or less life, he or she loses the game.

704.5b. If a player attempted to draw a card from a library with no cards in it since the last time state-based actions were checked, he or she loses the game.

704.5c. If a player has ten or more poison counters, he or she loses the game. Ignore this rule in Two-Headed Giant games; see rule 704.5u instead.

704.5d. If a token is phased out, or is in a zone other than the battlefield, it ceases to exist.

704.5e. If a copy of a spell is in a zone other than the stack, it ceases to exist. If a copy of a card is in any zone other than the stack or the battlefield, it ceases to exist.

704.5f. If a creature has toughness 0 or less, it’s put into its owner’s graveyard. Regeneration can’t replace this event.

704.5g. If a creature has toughness greater than 0, and the total damage marked on it is greater than or equal to its toughness, that creature has been dealt lethal damage and is destroyed. Regeneration can replace this event.

704.5h. If a creature has toughness greater than 0, and it's been dealt damage by a source with deathtouch since the last time state-based actions were checked, that creature is destroyed. Regeneration can replace this event.

704.5i. If a planeswalker has loyalty 0, it’s put into its owner’s graveyard.

704.5j. If a player controls two or more planeswalkers that share a planeswalker type, that player chooses one of them, and the rest are put into their owners' graveyards. This is called the "planeswalker uniqueness rule."

704.5k. If a player controls two or more legendary permanents with the same name, that player chooses one of them, and the rest are put into their owners' graveyards. This is called the "legend rule."

704.5m. If two or more permanents have the supertype world, all except the one that has had the world supertype for the shortest amount of time are put into their owners' graveyards. In the event of a tie for the shortest amount of time, all are put into their owners' graveyards. This is called the "world rule."

704.5n. If an Aura is attached to an illegal object or player, or is not attached to an object or player, that Aura is put into its owner’s graveyard.

704.5p. If an Equipment or Fortification is attached to an illegal permanent, it becomes unattached from that permanent. It remains on the battlefield.

704.5q. If a creature is attached to an object or player, it becomes unattached and remains on the battlefield. Similarly, if a permanent that’s neither an Aura, an Equipment, nor a Fortification is attached to an object or player, it becomes unattached and remains on the battlefield.

704.5r. If a permanent has both a +1/+1 counter and a -1/-1 counter on it, N +1/+1 and N -1/-1 counters are removed from it, where N is the smaller of the number of +1/+1 and -1/-1 counters on it.

704.5s. If a permanent with an ability that says it can’t have more than N counters of a certain kind on it has more than N counters of that kind on it, all but N of those counters are removed from it.

704.5t. In a Two-Headed Giant game, if a team has 0 or less life, that team loses the game. See rule 810, "Two-Headed Giant Variant."

704.5u. In a Two-Headed Giant game, if a team has fifteen or more poison counters, that team loses the game. See rule 810, "Two-Headed Giant Variant."

704.5v. In a Commander game, a player that’s been dealt 21 or more combat damage by the same commander over the course of the game loses the game. See rule 903, "Commander."

704.5w. In an Archenemy game, if a non-ongoing scheme card is face up in the command zone, and it isn't the source of a triggered ability that has triggered but not yet left the stack, that scheme card is turned face down and put on the bottom of its owner's scheme deck. See rule 904, "Archenemy."

No.