This decreases your odds of being mana flooded and of being mana screwed all at once, which is incredibly powerful
White has a bunch of effects like this that spread counters around your opponents creatures, like Noble Heritage and other taxing effects like Archangel of Tithes
Skyclave Relic is a decent enough mana rock
Its a risky but interesting addition to Azorius or Esper control decks that care about gaining life and have many cards in hand
The Xanathar Guild is made up of some of Waterdeep's most disreputable folk, as well as monsters forced into subservience or drawn to the beholder by the promise of treasure, food, or power
It feels like one of whites better creatures, not because its especially strong in and of itself, but because it can go in a variety of decks and generate card and board advantage in all of them