Illrigger spell - Vengeful Blade - would it break the targets concentration

The spell states:  On a hit, the target suffers the weapon attack’s normal effects and then radiates a dark aura of energy until the start of your next turn. If the target makes an attack or casts a spell before then, the target takes 1d8 necrotic damage and the spell ends.

Would the target need to roll for concentration if they cast a spell? (presuming they are casting a concentration spell).

Rolling for concentration would be moot because the ability says "the target takes 1d8 necrotic damage and the spell ends."

It's an interesting question. I'd go with the rules for simultaneous effects. Assuming the target is casting the spell on their turn, they can choose to take the damage first, thus not having to roll for concentration.

Quote from Davyd >>

Rolling for concentration would be moot because the ability says "the target takes 1d8 necrotic damage and the spell ends."

I think "the spell ends" is talking about the Vengeful Blade spell, not the spell the target is casting. It could be clearer, though.

The target would need to make a concentration check when they take the initial weapon attack, and one when they take the damage which is triggered when casting a spell.

The Vengeful Blade spell is what ends when the target casts a spell, not the spell cast by the target. The wording is the same for a lot of spells whose effects end on a condition.

Quote from wagnarokkr >>

Quote from Davyd >>

Rolling for concentration would be moot because the ability says "the target takes 1d8 necrotic damage and the spell ends."

I think "the spell ends" is talking about the Vengeful Blade spell, not the spell the target is casting. It could be clearer, though.

 Classic MCDM wording, clear as mud.

In that case, the target would need to make a concentration check against the 1d8 necrotic, same as any other damage source

Quote from Davyd >>

Quote from wagnarokkr >>

Quote from Davyd >>

Rolling for concentration would be moot because the ability says "the target takes 1d8 necrotic damage and the spell ends."

I think "the spell ends" is talking about the Vengeful Blade spell, not the spell the target is casting. It could be clearer, though.

 Classic MCDM wording, clear as mud.

In that case, the target would need to make a concentration check against the 1d8 necrotic, same as any other damage source

 Wouldn't it be nice to kill high level spells with cantrip though? Uh maybe too strong huh.

Quote from Frachese >>

It's an interesting question. I'd go with the rules for simultaneous effects. Assuming the target is casting the spell on their turn, they can choose to take the damage first, thus not having to roll for concentration.

 This can't be a real case of simultaneous effects as the casting of the spell has to actually occur to trigger the occurrence of the necrotic damage.

I'd say no because the target takes 1d8 necrotic damage target when it cast a spell, and Concentration occur after the spell is cast and take effect.

Quote from Wtfdndad >>

Quote from Frachese >>

It's an interesting question. I'd go with the rules for simultaneous effects. Assuming the target is casting the spell on their turn, they can choose to take the damage first, thus not having to roll for concentration.

 This can't be a real case of simultaneous effects as the casting of the spell has to actually occur to trigger the occurrence of the necrotic damage.

I agree with this.  The spell is successfully cast and takes effect.  Anything that happens when the spell takes effect successfully happens.  Then, a concentration check is made to maintain concentration thereafter.

Note that for a readied spell or a long casting time spell the concentration check would be made prior to the spell taking effect.