But that blocks diverse collection of multicolored cards, flexible lands, and powerhouse spells have since become staples in many Commander players favorite decks
I already mentioned a sizeable amount of the Spell cards, like "Iron Core of Koa'ki Meiru" (as cost for some card effects and to keep your monsters alive), "Diamond Core of Koa'ki Meiru" (searcher and destruction protection), "Fire Formation - Tenki" (another searcher) and "Core Overclock" (ATK steroid), but there are some more
Example: I would not want discard out of Lantern Control against Jund
Most notably, these premium missions unlock Premium Tickets, which can be used in turn to unlock rare cards that are otherwise unobtainable
The cards themselves are available from WotC directly, and some of them include codes for Arena versions of the same cards