The Ring is also quite useful even without all its abilities, although admittedly its true impact will also have a lot to do with who is carrying it
We have a variety of ways to keep triggering Kardur: the most common is by making token copies of Kardur with cards like Jaxis, the Troublemaker and Orthion, Hero of Lavabrink which trigger his mega goad before dying, but we also have bounce with Skull Collector and reanimate/blink with Rescue from the Underworld
What I normally would do before posting or accepting a trade is going into the trades wall, checking what users are asking, and giving in exchange for a card to get an idea
I mean, on his own he is effectively a 3-mana 3/3 in most cases, and youll often have other creatures on which you can use the ability that might have more of an impact
I like the design space that Necron Dynasties explores in mono-black, so divorcing the precons from the lore of their source material is something that I'd count as a win