While the effect of making a player lose the game by paying one mana of every color is a nice shortcut, since it requires your opponent to have ten or less life, most of the time you're better off saving that mana for spells since they'll be defeated soon anyways
Then again, someone looked up at Ursa Major and said looks like a bear to me! so I dont suppose its too far off
You can do even more explosive things with Narsets second ability
Its only one treasure in each turn, but if players across the table are in decks the predominantly draw cards in other peoples terms this could net you a solid 3 mana per turn cycle
To fill up your graveyard, Celes, Rune Knight and Mog, Moogle Warrior arrive with potent effects that get creatures into your graveyard, with the Celes also being her own wincon and value engine with her ability to grow your whole board every time a creature enters from your graveyard