Are Erinyes' Hellish Weapons poisonous in a PC's hands?

Question

So the entry for Erinyes has the following:

Hellish Weapons. The erinyes's weapon attacks are magical and deal an extra 13 (3d8) poison damage on a hit (included in the attacks).

Then we have the following entries for weapon attacks:

Longsword. Melee Weapon Attack: +8 to hit, reach 5 ft., one target. Hit: 8 (1d8 + 4) slashing damage, or 9 (1d10 + 4) slashing damage if used with two hands, plus 13 (3d8) poison damage.

Longbow. Ranged Weapon Attack: +7 to hit, range 150/600 ft., one target. Hit: 7 (1d8 + 3) piercing damage plus 13 (3d8) poison damage, and the target must succeed on a DC 14 Constitution saving throw or be poisoned. The poison lasts until it is removed by the lesser restoration spell or similar magic.

In a recent battle an Erinyes was disarmed via the battle master ability and lost possession of the longsword. Would this longsword retain its properties if used by a player character?

At first I was leaning towards no, as the description of 'Hellish Weapons' says that the attacks are magical and deal extra damage, not that the weapons themselves are magical. But then I noticed that the longbow had a different poison effect on its attacks, which would lead to thinking that the weapon imparted the poison effect.

The closest comparable weapon is the Flametongue, which requires attunement and deals an extra 2D6 fire damage (rare). Would this weapon be OP in the hands of characters? Would this be comparable to any other magic swords at the very rare or legendary tier?

Answer 1

No, a PC cannot make use of the devil's poison

The hellish weapon is a special trait of the creature, not of the weapon. Therefore, the trait only applies when the erinyes is wielding the weapon.

In addition, the trait specifies that "The erinyes’s weapon attacks are magical…" not that the erinyes's weapons are magical. The devil could just as easily hit a PC with a chair, and the improvised weapon would still deal poison damage.

Answer 2

No; the poison is a result of the Erinyes' ability.

Hellish Weapons is an ability of the Erinyes, and the damage from that is included in the statblock. This is not the only place this occurs, as all of the angels from the MM possess the similar Angelic Weapons ability that affects their weapon attacks.

However:

One possible thing to consider is the secondary poison effect of the Erinyes' bow. This inflicts the poison condition based on a saving throw, and doesn't occur elsewhere in the statblock. This could be evidence that this effect of the longbow could be used by PCs, but it could also be a specific poison on the arrowheads or just an unwritten unique ability of the Erinyes as opposed to part of the weapon. That is a distinction that must be made by each DM until more official evidence is given. My personal ruling would be that the secondary poison effect is due to poison or magic on the arrows; the PCs can use those arrows, but they are a limited resource like any other magic arrow.