Can I use Moonlace to allow a Lightning Bolt to target a creature with protection from red?

Question

The action of casting a spell is only apparently simple. There are many steps, and it is for this reason that I propose this question.

Taking into account rule 601.2a only (without taking into account the several successive steps, by now, and in particular without referring to the choice of targets which is however essential), which reads

To propose the casting of a spell, a player first moves that card (or that copy of a card) from where it is to the stack. It becomes the topmost object on the stack. It has all the characteristics of the card (or the copy of a card) associated with it, and that player becomes its controller. The spell remains on the stack until it’s countered, it resolves, or an effect moves it elsewhere.

and using at the same time the blue rare card Moonlace, I wondered if it was possible, by keeping priority, to use the latter card to make another spell colorless before making my choice of its possible targets.

For example, if I have a Lightning Bolt and I want to cast it on a creature with protection from red – e.g. Repentant Blacksmith – may I use Moonlace to make the Bolt colorless, thus allowing to legally target the Repentant Blacksmith – or, possibly, other cards that have the ability "protection from colored spells", too?

The question is set in an open way, because at the moment I don't know if the action described is or is not possible, based on my current knowledge of the rules. In other words, thinking about the question by myself, I don't think it is possible to cast the Lightning Bolt first and then the Moonlace, since for a correct casting of the Lightning Bolt I think it is included the choice of the target, which cannot be legal since the creature is protected from red. On the other hand, casting Moonlace first is all the same wrong, because the spell that should target doesn't exist yet, and therefore this action would be illegal too, for the same reason. That's the reason why I said to refer to rule 601.2a only.

The key to the question then is simply: is there someone knowing any “sleight of hand” to grant devoid ability on Lightning Bolt, before his target is chosen - via Moonlace, or via any other ways, otherwise? And, if that kind of sleight does exist, what spell should I cast first? It is possible to cast two spells simultaneously?

Answer 1

Moonlace only works on Lightning Bolt when it's a spell, i.e. an object on the stack. To get it there, you have to cast it, which includes specifying a legal target. As you indicated, Repentant Blacksmith isn't one.

What would work is casting the Lightning Bolt on another target (e.g. your opponent), Moonlacing it so it becomes colorless, and then change the target with another card, e.g. Misdirection.

Answer 2

No, that won't work. While you are in the process of casting a spell, you can't even begin casting another spell, let alone have that second spell resolve before you finish casting the first. If Lighning Bolt would have an illegal target from the start, it's not going to be on the stack to be modified by Moonlace.

As you already noted, the rules of casting a spell are quite extensive, and in most cases, the steps can be walked over because they are intuitive. However, in your scenario, we have to dig down a bit.

It's important to note here that casting a spell is a process. You follow the steps in the exact order described. There is no rule that would allow you to interrupt this process with any other action, in particular you can't begin casting a second spell while you are playing the first.

601.2a To propose the casting of a spell, a player first moves that card (or that copy of a card) from where it is to the stack. It becomes the topmost object on the stack. It has all the characteristics of the card (or the copy of a card) associated with it, and that player becomes its controller. The spell remains on the stack until it’s countered, it resolves, or an effect moves it elsewhere.

We can continue to targeting:

601.2c The player announces their choice of an appropriate object or player for each target the spell requires. [..]

The process of casting Lightning Bolt stops here, because a creature with protection from red is not an "appropriate" target for a red Lightning Bolt. The game returns to the point just before you proposed casting LB: You have priority, and the Bolt is in your hand rather than on the stack:

601.2e The game checks to see if the proposed spell can legally be cast. If the proposed spell is illegal, the game returns to the moment before the casting of that spell was proposed

If Lightning Bolt was legally cast, you would gain priority afterwards and thus the right to cast another spell if you wish, such as Moonlace. Of course, if Lightning Bolt would have been legally cast from the start, you wouldn't need Moonlace to make it legal.