With Kardur by your side, force your foes to squabble with one another, and finish them off one by one
You can pay seven mana to meld him with The Mightstone and Weakstone to create Urza, Planeswalker, who has a whopping five different abilities you can use - and you can choose to activate two abilities per turn instead of just one
Creature - Druid Squirrel Contaminant Grafter Trample, toxic 1 Whenever one or more creatures you control deal combat damage to one or more players, proliferate
Meanwhile the Sphinx can net you a free scry at the beginning of the first upkeep, which is nasty, and then when you drop it, you'll get a scry 1 for free each turn too
Lot of spiders are already good blockers, and with the addition of deathtouch theyre even better
With these cards no longer being in print and strict rules limiting their use in gameplay, owning a piece of this history is akin to holding a fragment of MTGs early legacy