What is the appropriate ability modifier for hurling a Javelin of Lightning?

Question

Is it Strength because it's a Thrown javelin (like a regular javelin), or Dexterity because of the wording of the descriptive text below? Specifically: 'make a ranged weapon attack' implies Dexterity to me.

This Javelin is a Magic Weapon. When you hurl it and speak its Command Word, it transforms into a bolt of lightning, forming a line 5 feet wide that extends out from you to a target within 120 feet. Each creature in the line excluding you and the target must make a DC 13 Dexterity saving throw, taking 4d6 lightning damage on a failed save, and half as much damage on a successful one. The Lightning Bolt turns back into a Javelin when it reaches the target. Make a ranged weapon Attack against the target. On a hit, the target takes damage from the Javelin plus 4d6 lightning damage.

The javelin's property can't be used again until the next dawn. In the meantime, the Javelin can still be used as a Magic Weapon.

Answer 1

"Make a Ranged Weapon Attack" does not imply a particular attribute. A javelin thrown with strength is still a "Ranged Weapon Attack". The Thrown property tells you what stat to use.

Thrown. If a weapon has the thrown property, you can throw the weapon to make a ranged attack. If the weapon is a melee weapon, you use the same ability modifier for that attack roll and damage roll that you would use for a melee attack with the weapon. For example, if you throw a handaxe, you use your Strength, but if you throw a dagger, you can use either your Strength or your Dexterity, since the dagger has the finesse property.

As odd as it may seem, a Javelin is actually a simple melee weapon according to p149 of the PHB. That means you use Strength. It does not have the Finesse property, so you may not use Dexterity.

The type of save required by the lightning bolt effect has no bearing on how the javelin itself is thrown. If it did, it would say so. It is worth noting that the target doesn't make a save - the wielder and the target are specifically excluded. The target takes the lightning damage on a hit.