Spectator Spell Reflection for Hail of Thorns?

Question

A Spectator (a lesser Beholder, described on Monster Manual p. 30) can use its reaction to use its Spell Reflection ability:

Spell Reflection. If the spectator makes a successful saving throw against a spell, or a spell attack misses it, the spectator can choose another creature (including the spellcaster) it can see within 30 feet of it. The spell targets the chosen creature instead of the spectator. If the spell forced a saving throw, the chosen creature makes its own save. If the spell was an attack, the attack roll is rerolled against the chosen creature.

My question is that if a ranger uses the spell Hail of Thorns and then hits the Spectator with an arrow, then if the Spectator makes its saving throw, can it redirect the thorns to another player?

The reason I question this is that the spell says that the thorns sprout from the ranged weapon or ammunition. In this sense, it seems that a person would have to have been hit by the arrow. However, other than this, the details of the Spell Reflection ability also suggest that it may be possible to make the thorns hit someone else even though it would still take the arrow damage.

Answer 1

Yes, the Spectator could "Reflect" the thorns

Lots of spells have stated physical sources of their damage. Fireball, perhaps the most famous D&D spell with a saving throw states that:

A bright streak flashes from your pointing finger to a point you choose within range and then blossoms with a low roar into an explosion of flame. (PHB, p. 241)

Whether or not damage from a spell has a physical source (a bright streak, thorns from an arrow, an explosion, or anything else) doesn't matter: all that is required is that a spell causes a Spectator to make a saving throw. If the spectator could only redirect a spell that has no physical source, or could only redirect it against a creature that was already in the spell's area of effect, the text of Spell Reflection would say so.

It is also worth noting that creatures in a spell's area of effect are typically considered "targets" of that spell. Note the table on page 249 of the DMG used to determine number of creatures in a spell's Area of Effect, entitled Targets in Areas of Effect. Also note that Jeremy Crawford has stated:

A typical area of effect has more than one target: the effect's point of origin and one or more creatures/objects.

Thus, although Hail of Thorns has a target of "self", those damaged by the spells are also considered "targets", and causing the spell to "target" another creature would make them eligible for the spell's damage.

Answer 2

No, because the Spectator has to save against the Spell itself, and the Thorns are not a spell in and of themselves

The spell Hail of Thorns does the following:

Target: Self

...

The next time you hit a creature with a ranged weapon attack before the spell ends, this spell creates a rain of thorns that sprouts from your ranged weapon or ammunition. In addition to the normal effect of the attack, the target of the attack and each creature within 5 feet of it must make a Dexterity saving throw. A creature takes 1d10 piercing damage on a failed save, or half as much damage on a successful one.

In this case, the spell doesn't actually target the Spectator, it buffs you. The enemy being shot is not the target of the spell and is not saving against the spell, it is saving against something the spell has created: essentially a bomb made of thorns.

For example, if a Caster launched Fireball at a Spectator and the Spectator succeeded, that would count as saving against a spell. But if Fireball was cast on the unstable cave ceiling above the Spectator, the Spectator might still make a saving throw, but if it succeeded, it couldn't retarget the rocks.

For another example, if a Caster attempted to Polymorph the Spectator, the Spectator could attempt to retarget the Polymorph if it succeeded on the Saving Throw. If the Caster Polymorphed an Ally into a creature, and that ally-creature missed the Spectator with an attack, the Spectator couldn't retarget Polymorph.

In this case, Hail of Thorns could not be retargeted because the Spectator is not saving against a spell, it is saving against a bomb which was made by a spell but is not itself a spell.

Edit: A Tweet from Crawford supports the idea that Hail of Thorns targets the Self and not the Spectator:

A range of self means the caster is the target, as in shield, or the point of origin, as in thunderwave (PH, 202)

https://twitter.com/jeremyecrawford/status/606193562317766656

Answer 3

Yes, the spectator can reflect hail of thorns

If the spectator makes a successful saving throw against a spell, or a spell attack misses it, the spectator can choose another creature...

Hail of thorns is a spell that causes a creature to make a saving throw:

The next time you hit a creature with a ranged weapon attack before the spell ends, this spell creates a rain of thorns that sprouts from your ranged weapon or ammunition. In addition to the normal effect of the attack, the target of the attack and each creature within 5 feet of it must make a Dexterity saving throw.

The spell effect is delivered by a ranged attack, but this does not matter. All that is required is that the saving throw that the spectator succeeds at is a result of a spell. If a saving throw is explained in the spell effect description it is part of the spell's effects, thus this saving throw and the thorns resulting from it are a direct effect of the spell. Thus, it meets all the criteria for the spectator's Spell Reflection ability.

Thus, if the spectator gets hit by an arrow under the effects of hail of thorns and makes its saving throw, it can redirect the thorns to another creature. It would still take the hit from the arrow though since that is a normal attack and not part of the spell.