So I was looking at UA and saw Raven Queen warlock. I was looking it over and I saw something interesting about the Sentinel Raven. It isn’t a familiar. This means if you take Pact of The Chain you get two familiars. Then if you get Invisibility you can cast it on the Sentinel Raven making it where you have two invisible familiars. This means both can take the Help action AKA you can give advantage to two attack rolls.