Does the Deflect Attack reaction of a Battle Smith artificer's Steel Defender impose disadvantage on all attacks from the chosen creature?

Question

In Eberron: Rising from the Last War, the artificer's Battle Smith subclass grants you a Steel Defender that can use its reaction to give disadvantage on a creature's attack roll.

The Steel Defender feature says:

It can move and use its reaction on its own, [...]

The Steel Defender's statblock lists the following reaction:

Deflect Attack. The defender imposes disadvantage on the attack roll of one creature it can see that is within 5 feet of it, provided the attack roll is against a creature other than the defender.

Does this disadvantage apply to all attacks by the chosen creature, or just to one of its attacks?

Answer 1

Just one of its attacks

Going by the wording used in the quote you provided, all of the language used to describe the chosen creature's attack is singular:

Deflect Attack. The defender imposes disadvantage on the attack roll of one creature it can see that is within 5 feet of it, provided the attack roll is against a creature other than the defender.

It appears as though, RAW, it only imposes disadvantage against one attack roll. This is also consistent with similar features, such as the Protection fighting style, which uses similar wording:

Protection. When a creature you can see attacks a target other than you that is within 5 feet of you, you can use your reaction to impose disadvantage on the attack roll. You must be wielding a shield.

Although you include the quote that it can "use its reaction on its own", remember that all creatures only have one reaction (unless explicitly stated otherwise), so the Steel Defender would only be able to use its Deflect Attack reaction once per round, and it would only regain the use of its reaction at the start of its next turn.