@Sami Padanius: Unlike aglar & egleria- which are derived directly from aklar(a) < KALAR, breged comes from ancient "BEREK-e-tē", which is clearly an earlier approach to Sindarin's gerund suffix -ed < -itā. That is to say, direct verbal derivations from BEREK would rather be breitha- (which is indeed attested), and *bregia- (although we lack attested verbs with "...gia...", possibly due to "initial kj/gj > k/g", occurring medially), or perhaps *breg- directly. In any case, I find BEREK "wild, fierce, violent, sudden" to be a fitting root for deriving "to attack". What I used was KOT(H) > oktā- > oktʰā- > oxþa- > oiþa- > oeþa- = *oetha- "to be hostile (towards), attack" (although it is more like "to make war", a connection which is shared by NDAK derivatives, so it can be overlooked with a semantic shift argument).
until someone tells me that we know how to form more than one past tense in Sindarin
Not sure what exactly you mean by this. But regardless, it would be safe to say that we do indeed know about past formations in more than one flavour.
I like using NDUL. I dislike dagnir, as with most late compounds for what should be early concepts, hence my *dangron (<NDAnKrō-ndō). I would have used *dagor (<NDAKrō) but it clashes with the attested dagor (<NDAKrō as well, though it should be *NDAKrē) which is "battle". So if I use NDUL as well, I would say *doldangron.