Nightmares aside, Thieving Amalgam is a nice way to steal and use your opponents cards against them in the eternal formats
Since it creates a token with only 100 attack power in attack position, there is a high probability that it will be targeted in the next turn
So if you have Summon: Bahamut in play with one lore counter, and you proliferate it twice to land on Chapter III (draw two cards), you'll also get to trigger Chapter II (destroy a creature)
Also the solo battle rewards suck
Deadly Rollick might not be the best of the Commander free spells (that would be Fierce Guardianship), but it still feels devastating when you cut off somebodys combo or remove their best creature with no mana
Although this is dropping on card resources, having Diablo on the board as early as possible will draw us more cards, generating resource value