Most of the legends matter stuff is on a handful of underperforming rares though (i.e., Clive's Hideaway, Serah Farron), so dont expect to build around legends specifically
Brimaz, Blight of Oreskos looks like it fits in the same category, though its more of a self-contained engine in an artifact-heavy deck than a full-on Phyrexian commander
In a deck with a low curve, it is quite easy to cast two spells per turn
However, if Everflowing Chalice has no charge counters on it, activating its last ability won't produce any mana
Dawn, Warriors Legacy Mizzix's Mastery is a cool build-around that can go nuts in the right deck
She also lets you draw a card at the end of every players turn if any player loses 4 or more Life that turn, which given the multiplayer nature of Commander, could reward you if others are playing well (or poorly)