You can use Blessings of Nature to put a counter on four creatures to get four triggers
Its the most iconic by a longshot, and one of MTGs most consistently good-but-not-broken cards, but that does put it just below the truly broken cards
It feels good to outright kill something with it, but it feels even better to put it on a creature that doesnt die because the Aura usually does enough to make that creature irrelevant while it also starts quickly pressuring your opponents life This is a pretty nice sacrifice outlet, and Black in this format has access to many rat tokens that will feel particularly good to sacrifice to this You cant build a dedicated discard deck in this format Paying a total of 8 mana for an extra combat step a good way to lose
Similarly, using Mikaeus in conjunction with Putrid Goblin and Ashnods Altar makes it trivial to generate infinite mana
it only interacts with a specific sets theme and is not compatible with the game at large
No matter what your tribal theme, I'd suggest putting one or all of these colourless cards in your deck