Does spiritual weapon continue to attack a creature if it turns invisible after the initial casting?

Question

We had this come up in our last game. The cleric was dumping multiple instances of spiritual weapon against the BBEG while bottlenecking the minion stack and protecting the backline. On the round following the third casting of spiritual weapon the BBEG pulled out a scroll of invisibility and turned himself invisible to make the "Grand Escape".

Now, the DM in this case ruled that spiritual weapon was allowed to continue attacking the BBEG because all three instances of the spell had set the BEEG as its target BEFORE the creature went invisible. But with that ruling, everyone was honestly confused on weather or not spiritual weapon "Cares" if the creature is invisible for the 50% miss chance due to concealment.

Can anyone give a clear RAW interpretation on how to correctly run the sequence of interactions:

1. Cleric casts spiritual weapon on a valid target.
2. Target later becomes invisible.

So, does spiritual weapon get to continue attacking the invisible target? And if so, how is it handled?

Answer 1

Reasonably sure there is no clear rule explicitly written to cover this case. Spiritual weapon didn’t get a lot of commentary outside its own spell description. This seems to be a case that they either never considered, or just left up to the DM.

But the clearest I can come up with is that this combination of statements suggest that despite looking like, and doing the damage of, some weapon, it isn’t really, mechanically, a floating weapon that makes attacks—it’s just a spell effect.

It strikes as a spell, not as a weapon

The weapon always strikes from your direction.

you can use a move action to redirect the weapon to a new target.

On any round that the weapon switches targets, it gets one attack. Subsequent rounds of attacking that target allow the weapon to make multiple attacks if your base attack bonus would allow it to.

Even if the spiritual weapon is a ranged weapon, use the spell’s range, not the weapon’s normal range increment, and switching targets still is a move action.

Particularly the fact that the spell never discusses the weapon needing to move around—even if your target moves, if you don’t redirect the spell, it still gets a “full attack” where an actual creature would have to move and thus not get a full attack.

So this seems, to me, to indicate that your DM made the right call, spiritual weapon can keep making attacks against a foe who turns invisible, without any risk of losing track of where that foe is. It doesn’t, however, tell you where the foe is? So you can’t just follow the spiritual weapon around and attack into the same square it is, seems like.

On the subject of the 50% miss chance, though, I’m pretty sure that would apply—ultimately, this is a spell attack, the cleric’s spell attack, and those are subject to that miss chance.