Especially in multiplayer formats like Commander, having your full mana pool and complete array of blockers primed for your opponents' turns is so useful
Not only is Anti-Venom immune to damage, it can also instantly resurrect something, burping up whatever strong creature is in your graveyard as soon as it comes down
Liliana and Grim Flayer work so well together, the combination of the two cards really makes this entire deck
As a commander, he gives you access to Green's suite of +1/+1 counter and fight effects, letting you weaponize his beefy frame while keeping the board in check
And since you always want to be able to find the right answer at the right time, a great Mono-Blue Commander should be able to keep the cards flowing and make sure you are never just sitting around with a handful of Islands
I wanted the problem statement to be something with relatively defined edges, and one that had some personal significance to the folks who are working on it