As a five-color commander, there is a lot of flexibility in how to build a Kenrith, the Returned King deck
It's a very strategic spell that can allow for massive card advantage given enough time
Not only does the deck already play Ephemerate/Phelia/Flickerwhisp, meaning you can often keep the Sphynx in play from turn three, but its also an important tool, since Esper topdeck is often dead interaction, and playing Solitude means youre often left with few cards in hand
Once you inevitably start exploring formats outside of just Standard or Modern and dig through older cards, promos, bonus sheets, serialized cards, alternate treatments, and whatever stunning nonsense Wizards decided to put in Collector Boosters this time around, rarities will start looking a bit messier
Vraska's ultimate gets an opponent to nine poison counters, and a single attack or proliferate will finish things off from there