Does Shield Master only grant DEX save bonuses vs. single-target spells?

Question

The second effect of the 5e feat "Shield Master" reads (emphasis mine):

If you aren't incapacitated, you can add your shield's AC bonus to any Dexterity saving throw you make against a spell or other harmful effect that targets only you.

The wording here is ambiguous. Does the bolded text only apply to the "or other harmful effect" part, or does it apply to the "a spell or other harmful effect" part? Applying the first reading leads to many scenarios that are logically questionable, but fully plausible under action-movie physics (hiding behind a big shield to avoid the AoE of a fireball), and some scenarios that are absurd (like ducking behind your shield to avoid a Lightning Bolt, a spell that explicitly travels through all creatures and many obstacles).

On the other hand, applying the second reading removes almost all utility from this portion of the feat. IMO, the rest of the feat alone isn't worth the ASI trade-off for the vast majority of characters. Off-hand, I can't think of any single target spells that offer a DEX save. Is there an official ruling on which reading of the feat is correct?

Answer 1

The second benefit of the Shield Master feat (PHB, page 170) does indeed only work against single-target spells.

From the rules on spell targets (PHB, page 204):

A typical spell requires you to pick one or more targets to be affected by the spell's magic. A spell's description tells you whether the spell targets creatures, objects, or a point of origin for an area of effect (described below).

Most AoE spells target a point in space, not (just) a creature. This is also mentioned in passing in the description of the range of a spell (PHB, page 202):

For a spell like fireball, the target is the point in space where the ball of fire erupts.

As a side note, I had a similar reaction, and built a list of the spells that Shield Master actually does work for.

Answer 2

The 2nd benefit of the Shield Master feat (PHB, p. 170) says:

If you aren't incapacitated, you can add your shield's AC bonus to any Dexterity saving throw you make against a spell or other harmful effect that targets only you.

So you do not gain the save bonus for AoE spells.

However, the third benefit of the spell does apply to AoE spells, effectively giving you Evasion from AoE spells for all points in space in the same area/same direction over the remainder of the turn:

If you are subjected to an effect that allows you to make a Dexterity saving throw to take only half damage, you can use your reaction to take no damage if you succeed on the saving throw, interposing your shield between yourself and the source of the effect.

Since half of the reaction spells last for the remainder of the turn, like Shield and Feather Fall, and as long as additional AoEs are coming from the same point in space, your shield effect should continue providing this Evasion effect.

So there are maybe 6 spells that qualify for the 2nd part of the feat - but a lot more that qualify for the 3rd part of the feat, since it includes all spells that require a Dexterity saving throw.

Just don't confuse the two parts of the feat!