yes, he is. You run the list with Food Chain + Misthollow Griffin / Eternal Scourge / Squee, the Immortal and then use Niv to dig through your deck to get something like Circu, Dimir Lobotomist and then keep recasting Niv to exile your opponents' libraries.
Though basically directly after Niv came out, The First Sliver was released which meant that while there was some Niv hype, it very quickly died off.
August 7, 2019 2:41 a.m.
"When Niv-Mizzet Reborn enters the battlefield, reveal the top ten cards of your library."
"For each color pair, choose a card that's exactly those colors from among them."
So there are 10 colour pairs total, White/Black, White/Blue, etc. This basically says: "pick up to one card from each of those colour pairs within the 10 cards you're looking at".
This means that if you saw two White/Blue cards, you could only pick one. Because it also says "exactly", this means that just becasue a card contains those colours doesn't mean you can pick it. So if you revealed a White/Blue/Red card, you couldn't pick it because it's not exactly two colours.
"Put the chosen cards into your hand and the rest on the bottom of your library in a random order."
Again, pretty self-explanatory.
So there you go. Becasue Niv is from Ravnica which focuses on the guilds, so does his ability. But they didn't want to just have him grab just any 10 multi-coloured cards (because that would be broken good), so they added some clauses about what you could get.
August 7, 2019 3:40 a.m. Edited.
You basically play 2 color goodies and run a Lot of mana fixing.
August 9, 2019 11:32 p.m.
Monomanamaniac how many lands would I have in the niv deck?
August 9, 2019 11:38 p.m.
I've never built one in commander but it depends on your budget, if you could afford a bunch of shock lands you'd have to run far less. Just keep in mind that lands are dead draws with your commander, so don't go too heavy. You'll want things that fetch lands, even just basic ones. Mana rocks are good to, though they too are dead draws to your commander. I'd probably stay somewhere in the 34-38 mana range
August 10, 2019 12:04 a.m.
Your goal is to have all 5 colors by at least turn 6, run 2 color cards (ie ravnica) that can benefit from your commander, and do big turns with him. Use whatever mechanic you want to make (bounce or preferably blink) to get repeated triggers and win off of explosive card advantage.