The two modes are interesting, but I wonder whether they have the same chance of being used. If one mode is used far more often than the other, a modal effect is not the right way to go IMO.

Best used with kicker? IDK.

Black is not supposed to get just any type of card from the graveyard, so I would put this down as . But even better would be a restriction of card types.

I worry most about this returning instant/sorcery cards, as those are the kings of repetitive game play if recurred. And a spell costing e. g. won't cost all that much life with the second mode either.

This is the kind of card that greatly benefits from triggering at the beginning of the precombat main phase.

Black can kinda do anything as long as it pays life right? If you are recurring X cost spells then I just see that as good deckbuilding.

Black can't do anything by paying life. While black has instances where it could recur other card types, the ones I've seen were permanents where that permanent type was more prominent than normal, such as two that could recur artifacts in Kaladesh block Brother's War, and one that could recur planeswalkers in War of the Spark. Still, both of those are permanents and closer to overlapping white and green.
Like SecretInfiltrator, I worry about instant and sorcery recursion, which is in blue and red's slices (green could formerly do that, but has since been narrowed to just permanent cards).