Classically good with Kediss, Emberclaw Familiar to try to kill the whole table at once, pairings with Ardenn, Intrepid Archaeologist to pants up for casual tables and Silas Renn, Seeker Adept for a fast mana Ad Nauseam (what else?) in cEDH are more likely duos
When you play a tutor that just grabs a creature, such as Eladamri's Call, people arent going to become too upset since you arent doing anything like cheating a creature into play via Tooth and Nail or dropping it with a Show and Tell or something similar
Then you tack on some planeswalker abilities and you have a card thats worth getting stoked about
All three of Ugin's abilities play very well in Casual Land
It's unclear whether this was the most necessary of the Slivers, but it was the one that frustrated the most opposing plans to deal with the problem and even opened up new game plans when the card advantage resulting from saving your creatures could allow Sliver decks to go the control route when backed up by counters and removal spells
Do You Need A Binder