I realize a lot of it is momentum from D&D, but the depiction of the banshee (bean sidhe if you want to be stick to Gaelic spelling) is definitely a bit off. With my luck, a holdover from Gygax's own philosophical slants about mortality in general. Still, assuming the morrigna isn't somehow holding it (mostly because of the phonetic similarity to Morrigan), I wonder if there's a place for a non-malicious banshee-equivalent that's truer to the Gaelic original. Fortunately, there's a name of a similar entity to the bean sidhe still untaken according to the Archives of Nethys--caoineag, the Scottish equivalent. (There's also the testier caointeach of Islay, who isn't above hobbling those who try to stop her warnings.) The fun bit will be paralleling caoineags and banshees that establishes a subtle, but extremely important, distinction in how they come about, if desired.