Felwar Stone is often better than a Signet in multiplayer games, and since you'll occasionally want mana of different colors, it's a nice mana rock to have
Chaos: Whenever you roll Chaos, Scry X, where X is the number of creatures removed from the game by Sumeriosis
Deathtouch Another way to discourage blocking is by giving a creature deathtouch, especially if the creature is small and will just come back from the dead anyway like Bloodsoaked Champion or Reassembling Skeleton or from Ravos, Soultenders triggered ability
You can get some especially good value if you already have a Birgi out and cant cast another because of the legend rule
What affects the value of Akawalli, the Seething Tower
Deck Ratios at a Glance Your 100 cards break into predictable slots