not only does the danger of their ultimates burn ever brighter
and Progenitus
Rites of Flourishing is a group hug card that helps all players equally, but it creates a problem in other strategies because you spend your mana on a card that helps everybody
(In that case, since Fuse doesn't apply, it acts like a normal split card - you can flash back either half, for its mana cost, ignoring the other half.) For more descriptions of how Fuse works, see its section in the official Mechanics of Dragon's Maze article.
But there are larger cards that want you to sacrifice them, like Prowling Geistcatcher and Corpse Augur, and those seem a perfect fit for Shadow, Mysterious Assassinone of the few sacrifice commanders that benefit when your lambs are large
Theres great mana fixing to make decks better, and there are powerful cards that can be played in multiple formats