Arcane Proxy

Casting a prototyped spell isn't the same as casting it for an alternative cost, and an alternative cost may be applied to a spell cast this way. For example, if an effect allows you to cast an artifact card without paying its mana cost, you could either cast Blitz Automaton normally, or as a prototyped spell.

If you don't want to cast the copy, you can choose not to; the copy ceases to exist the next time state-based actions are checked.

If you cast a spell "without paying its mana cost," you can't pay any alternative costs. You can, however, pay additional costs, such as kicker costs. If the card has any mandatory additional costs, you must pay those.

The prototype ability functions in any zone that the spell could be cast from. For example, if an effect allows you to cast artifact spells from your graveyard, you could cast a prototyped Blitz Automaton from your graveyard.

When cast as a prototyped spell, that spell has the mana cost, power, and toughness characteristics shown in its colored, secondary text box rather than the normal values of those characteristics. Its color and mana value are determined by that mana cost. The permanent that spell becomes as it resolves has the same characteristics. If the spell leaves the stack in any other way, or the permanent it becomes leaves the battlefield, it immediately resumes using its normal characteristics.

A prototype card is a colorless card in every zone except the stack or the battlefield, as well as while on the stack or the battlefield if not cast as a prototyped spell. Ignore its alternative characteristics in those cases. For example, while it's in your graveyard, Blitz Automaton is a colorless creature card with mana value 7. It can't be the target of Recommission, a spell that targets an artifact or creature card with mana value 3 or less in your graveyard.