As long as you control three or more legendary creatures, Kolvori gets +4/+2 and has vigilance.

{1}{G}, {T}: Look at the top six cards of your library. You may reveal a legendary creature card from among them and put it into your hand. Put the rest on the bottom of your library in a random order.

As The Ringhart Crest enters the battlefield, choose a creature type.

{T}: Add {G}. Spend this mana only to cast a creature spell of the chosen type or a legendary creature spell.