For my money, it’s acc. of motion towards, but you should use the preposition - ad vos confugio. (It’s OK to omit ad with proper nouns or the common nouns urbs, domus and rus, but none of these applies here.)
We usually translate Latin dative as “to (noun)”, but the converse isn’t necessarily true. (Long disquisition about actor roles in various languages omitted here on the grounds of paralyzing tedium).
Mind you, I ----ed up the nom. plu. of magnum opus only the other day, so maybe you should take my opinion with a grain of salt.
Let me guess, you mistook opus as a second declension noun, thus a plural of opi, rather than operes, which I think is correct, right? Anyways, to the best of my recollection, which is hazy, you are correct about the original matter.
Even more embarrassing - remembered it was 3rd declension (yes, plural is opera), but then thought (using the word “thought” in its loosest possible sense): “oh, and magnus is a 1st/2nd declension adjective, so the neuter plural is bound to be the same as the masculine, isn’t it?” (Maybe in German, pal…)
My Latin teacher is still alive, so she can’t turn in her grave…
Incidentally, since absolutely nobody asked, I’ll expand a bit on the need for ad. The accusative case is normally used for the direct object in a sentence (the patient, to use the more general term - whoever or whatever is on the receiving end of whatever process the sentence is describing). However, the accusative is also used, as noted, to indicate “motion towards”. In most instances (I first typed “most cases”, there, but that’s a whole different can of worms) you need the preposition ad (“to”) to make it quite clear you’re talking about the motion. You don’t need it if your listener would automatically assume you were talking about the motion - as s/he would if you used a) the name of a place or b) one of the three common nouns mentioned above - urbs (“city”), domus (“house”) or rus (“country”).
Well, now I feel pretty dumb too. Of course it’s opera. I believe the word even made its way into English. On the other hand, I last took (or really cared much about) Latin about six years ago, and was never all that great it. Hell, my high school diploma was written in Latin, and I still haven’t figured out what it says.