Gaining life and growing all your durdles is a pretty disgusting effect to tack onto a not-completely-horrendous evasive body, and since it triggers on ALL life gain, its inherent synergies are pretty absurd
Paying X to make everyone mill, before making a ton of 2/2 Zombie tokens can quickly turn the game in your favour
Its all about value, drawing cards, setting up powerful synergies, and using your tech upgrades to take over the board
On top of being a good card, The Endstone is also a major plot element to Edge of Eternities' story, being the plot device that drives the unique "choose your own adventure" style, as it can rewrite time to achieve what it wants
Magic: The Gathering Arenas economy can be a tricky thing to work around