If such a spell is copied, and the effect that copies the spell allows a player to choose new targets for the copy, the number of targets can't be changed. The player may change any number of the targets, including all of them or none of them. If, for one of the targets, the player can't choose a new legal target, then it remains unchanged (even if the current target is illegal).
You choose how many targets each spell with a strive ability has and what those targets are as you cast it. It's legal to cast such a spell with no targets, although this is rarely a good idea. You can't choose the same target more than once for a single strive spell.
The tokens copy exactly what was printed on the original creature and nothing else (unless that permanent is copying something else or is a token; see below). It doesn't copy whether that creature is tapped or untapped, whether it has any counters on it or Auras and Equipment attached to it, or any non-copy effects that have changed its power, toughness, types, color, and so on.
Magic: The Gathering · ™ & © Wizards of the Coast · Illus. Sean Vo
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If a spell or ability allows you to cast a strive spell without paying its mana cost, you must pay the additional costs for any targets beyond the first.
Any enters-the-battlefield abilities of the copied creature will trigger when the token enters the battlefield. Any "as [this permanent] enters the battlefield" or "[this permanent] enters the battlefield with" abilities of the copied creature will also work.
If all of the spell's targets are illegal when the spell tries to resolve, it won't resolve and none of its effects will happen. If one or more of its targets are legal when it tries to resolve, the spell will resolve and affect only those legal targets. It will have no effect on any illegal targets.
If the copied creature is a token, the token created by Twinflame copies the original characteristics of that token as stated by the effect that put that token onto the battlefield.
If the copied creature has {X} in its mana cost, X is considered to be 0.
The tokens see each other enter the battlefield. If any of them have a triggered ability that triggers whenever a creature enters the battlefield, they'll trigger for one another.
If the copied creature is copying something else (for example, if the copied creature is a Clone), then the token enters the battlefield as whatever that creature copied.
If another creature becomes or enters the battlefield as a copy of the token, that creature will have haste, but you won't exile it. However, if Twinflame creates multiple tokens copying a single creature due to a replacement effect (like the one Doubling Season creates), you'll exile each of them.
The mana cost and mana value of strive spells don't change no matter how many targets they have. Strive abilities affect only what you pay.
