One of my current players has the first Wizard Evoker for whom I have GMed.
His PC's Sculpt Spells ability was easy to interpret at lower levels, when his evocation spells, like thunderwave and fireball, were instantaneous.
As he advances, however, he may obtain spells that have longer durations, such as Storm Sphere, Wall of Ice, or Whirlwind. I am realizing that I do not know how to adjudicate Sculpt Spell with spells that persist, especially when the initial conditions of the Sculpt Spell ability no longer apply.
Sculpt Spells says:
Beginning at 2nd level, you can create pockets of relative safety within the effects of your evocation spells. When you cast an evocation spell that affects other creatures that you can see, you can choose a number of them equal to 1 + the spell’s level. The chosen creatures automatically succeed on their saving throws against the spell, and they take no damage if they would normally take half damage on a successful save.
Storm Sphere, for example, has a a duration of Concentration (up to 1 minute) and says in part:
Each creature in the sphere when it appears or that ends its turn there must succeed on a Strength saving throw or take 2d6 bludgeoning damage.
To use the Sculpt Spell ability, the Evoker must see the creatures he is designating as being protected at the time he casts the Storm Sphere, and they must be in the area of the sphere at the time he casts it. It is clear that designating the protected creatures happens "when you cast".
What is not clear to me is whether this protection can be lost if the creatures no longer meet the conditions that were required for them to be designated as protected. That is, is their protection, once established, automatically maintained for the duration of the spell, or is it continually maintained by the Evoker and subject to them continuing to fulfil the conditions of its establishment?
For example, what would happen to a protected creature if it was to exit the area of the Sphere and later re-enter?
Does the Evoker need to maintain them in his sight to maintain their protection? If they were originally protected when the spell was cast, but later became invisible, would it end their protection if the Evoker could no longer see them?
It is possible that reviewers may mark this as asking multiple questions. To be clear, I see them as examples of one question - Under what conditions does the protection afforded by Sculpt Spell persist or not persist over time?
A question about Melf's Minute Meteors has some of the same concerns as my question, and the accepted answer to that question includes a tweet quote from Jeremy Crawford specifically about Storm Sphere. (Thanks to Medix2 for pointing out the question; note that the tweet itself comes from when such tweets were official rulings, while the post does not). In the (now-unofficial) tweet, Crawford says that the intent was for the Sculpt Spell ability to be used only on the turn the spell is cast. However, he admits that RAW it can be used on subsequent turns.
My question is not a duplicate of that question because:
That question is about Melf's Minute Meteors which has the complicating issue of potentially not having any creature affected by it at the time it is cast. This question assumes that "When you cast an evocation spell that affects other creatures that you can see," means that Sculpt Spell works only on creatures affected by the spell on the round you cast it.
The question that Crawford responded to about Storm Sphere was "Evo. wiz casts Storm Sphere and uses Sculpt Spell on ally in effect. Ally succeed on future saves while remaining in sphere?" Crawford's tweet did not address this question of a protected creature leaving the area of effect and returning (one possibility for no longer meeting the initial conditions of protection).
The question that Crawford responded to about Storm Sphere did not address the issue of the Evoker losing sight of the protected creature (another possibility for no longer meeting the initial conditions of protection).
