As long as you control three or more legendary creatures, Kolvori gets +4/+2 and has vigilance.
1G, 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.
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The Ringhart Crest
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.