Saheeli, Radiant Creator
Legendary Creature — Human Artificer
Whenever you cast an Artificer or artifact spell, you get 
(an energy counter).
At the beginning of combat on your turn, you may pay . When you do, create a token that's a copy of target permanent you control, except it's a 5/5 artifact creature in addition to its other types and has haste. Sacrifice it at the beginning of the next end step.
Ernanda Souza
Rulings
Any abilities of the copied permanent that trigger when that permanent enters will trigger. Any “as [this permanent] enters” or “[this permanent] enters with” abilities of the chosen permanent will also work.
(wotc • 2025-02-07)
Energy counters aren’t mana. They don’t go away as steps, phases, and turns end, and effects that add mana “of any type” can’t give you energy counters.
(wotc • 2025-02-07)
Energy counters are a kind of counter that a player may have. They’re not associated with any specific permanents.
(wotc • 2025-02-07)
Keep track of how many energy counters each player has. Potential ways to track this include writing them down on paper or using dice, but any method that is clear and mutually agreeable is fine.
(wotc • 2025-02-07)
If an effect says you get one or more {E}, you get that many energy counters. To pay one or more {E}, you lose that many energy counters. You can’t pay more energy counters than you have. Any effects that interact with counters a player gets, has, or loses can interact with energy counters.
(wotc • 2025-02-07)
Some spells and abilities which give you {E} or say you “may pay” some amount of {E} require one or more targets. If each target chosen is an illegal target as that spell or ability tries to resolve, it won’t resolve. None of its effects will happen, you won’t get any {E} from it, and you won’t get the chance to pay any {E} for its effects even if you want to.
(wotc • 2025-02-07)
{E} is the energy symbol. It represents one energy counter.
(wotc • 2025-02-07)
The token you create copies the original characteristics of the permanent as printed on the card or, for a token, as stated by the effect that created that token (unless it’s copying something else; see below). It doesn’t copy whether that permanent is tapped or untapped, whether it has any counters on it or Auras or Equipment attached to it, or any non-copy effects that have changed its power, toughness, types, color, and so on.
(wotc • 2025-02-07)
Some spells and abilities say that you “may pay” a certain amount of {E}. You can’t pay that amount multiple times to multiply the effect. You simply choose whether or not to pay that amount of {E} as the ability resolves.
(wotc • 2025-02-07)
If the copied permanent has {X} in its mana cost, X is 0.
(wotc • 2025-02-07)
If the copied permanent is copying something else, then the token enters the battlefield as whatever that permanent copied.
(wotc • 2025-02-07)
Some spells and abilities say that you “may pay” a certain amount of {E}, then describes an effect that happens “if you do.” In that case, no player may take actions to try to stop the ability’s effect after you make your choice. If the payment is instead followed by the phrase “when you do” followed by an effect, then after you choose to pay {E}, a new triggered ability called a reflexive trigger is put on the stack, and you choose targets for the reflexive trigger (if the effect asks for targets). Players may respond as normal to this new triggered ability. Once that reflexive trigger resolves, the effect will finally occur.
(wotc • 2025-02-07)
Rulings
Any abilities of the copied permanent that trigger when that permanent enters will trigger. Any “as [this permanent] enters” or “[this permanent] enters with” abilities of the chosen permanent will also work.
(wotc • 2025-02-07)
Energy counters aren’t mana. They don’t go away as steps, phases, and turns end, and effects that add mana “of any type” can’t give you energy counters.
(wotc • 2025-02-07)
Energy counters are a kind of counter that a player may have. They’re not associated with any specific permanents.
(wotc • 2025-02-07)
Keep track of how many energy counters each player has. Potential ways to track this include writing them down on paper or using dice, but any method that is clear and mutually agreeable is fine.
(wotc • 2025-02-07)
If an effect says you get one or more {E}, you get that many energy counters. To pay one or more {E}, you lose that many energy counters. You can’t pay more energy counters than you have. Any effects that interact with counters a player gets, has, or loses can interact with energy counters.
(wotc • 2025-02-07)
Some spells and abilities which give you {E} or say you “may pay” some amount of {E} require one or more targets. If each target chosen is an illegal target as that spell or ability tries to resolve, it won’t resolve. None of its effects will happen, you won’t get any {E} from it, and you won’t get the chance to pay any {E} for its effects even if you want to.
(wotc • 2025-02-07)
{E} is the energy symbol. It represents one energy counter.
(wotc • 2025-02-07)
The token you create copies the original characteristics of the permanent as printed on the card or, for a token, as stated by the effect that created that token (unless it’s copying something else; see below). It doesn’t copy whether that permanent is tapped or untapped, whether it has any counters on it or Auras or Equipment attached to it, or any non-copy effects that have changed its power, toughness, types, color, and so on.
(wotc • 2025-02-07)
Some spells and abilities say that you “may pay” a certain amount of {E}. You can’t pay that amount multiple times to multiply the effect. You simply choose whether or not to pay that amount of {E} as the ability resolves.
(wotc • 2025-02-07)
If the copied permanent has {X} in its mana cost, X is 0.
(wotc • 2025-02-07)
If the copied permanent is copying something else, then the token enters the battlefield as whatever that permanent copied.
(wotc • 2025-02-07)
Some spells and abilities say that you “may pay” a certain amount of {E}, then describes an effect that happens “if you do.” In that case, no player may take actions to try to stop the ability’s effect after you make your choice. If the payment is instead followed by the phrase “when you do” followed by an effect, then after you choose to pay {E}, a new triggered ability called a reflexive trigger is put on the stack, and you choose targets for the reflexive trigger (if the effect asks for targets). Players may respond as normal to this new triggered ability. Once that reflexive trigger resolves, the effect will finally occur.
(wotc • 2025-02-07)