This can be critical in particular considering that a lot of your Characters will need to be banished to remove opponent threats
Blue is often added for its many cantrips, defensive counterspells, and hyper-efficient draw like Windfall or Echo of Eons
While the flexibility these abilities offer is already quite powerful, unlike other Planeswalkers that may only activate one ability per turn, you can instead activate two of Urza's abilities during each of your turns
Despite these restrictions, there were still a ton of great cards that didnt make the cut
This drastically lowers the cost of the deck compared to others that contain 10 or more mythic rares, and due to multicolor mana requirements, tons of regular rare cards
If an opponent tries to remove it, the presence of its Ward - Pay 7 Life ability will essentially give it an eighth keyword: haste, and attacking into it is almost impossible to do profitably