One of the big challenges we had to solve in design was addressing some of the issues with tribal decks. We already discussed one of them earlier, which is that the creature density you need to build a tribal deck conflicts with what tends to be good in Commander.
One other issue we found with building tribal decks is that sometimes you have to fill your deck with cards you wouldn't normally play in Commander. For example, if you build a Cats deck, the first handful of Cats might be great, but by the end you might end up playing a couple Cats you're less than thrilled about. This means you're going to need a bit of extra incentive to want to play with them. And, plus, we want to make sure you have enough creatures.
We investigated several different mechanics and eventually came up with something that made you want to play a tribe because it affected everything about your deck. It wasn't just this one card that was awesome—this commander made your entire deck more awesome simply by being your commander.
It was called "coach" in design. You'll get to know it as eminence.
[...]
Okay, now let's talk about eminence.
It puts tribal front and center, making the decks loudly tribal and creating inherent tribal gameplay. Every game you play using a creature with eminence as your commander is going to make you care about your tribe. It's awesome.
Now, I know what past card you're probably comparing eminence to. And it's this guy.
Oloro is not a card I'm particularly fond of. He's another guy in the same space, granting you a bonus from the command zone. So what gives? Why is Oloro a card I cringe at while eminence is something I'm happy to put in the set?
Well, there's a big key difference.
Oloro works in any deck from the Command Zone, providing something incrementally every turn without caring at all about what you're doing. It doesn't have any kind of deck-building restriction.
With eminence, on the other hand, you actually have to do something to make it good. You're paying a cost of building your deck in a certain way. Additionally, unlike Oloro, which simply awards you life every turn, eminence impacts cards you actually play, meaning they're as removable as anything else. Yeah, I can play my Dragons for cheaper, but you can still deal with my Dragons all the same. It just helps make some Dragons playable that are one mana too expensive.