This card does for Calvin Wright what no amount of soak can do: prevents him from dying to direct damage/horror. (You can't always draw Until the End of Time, and even that can only take so much of a beating.)
It's extra insurance against surprise bursts of damage once you've maxed out his statline, and if paired with the myriad A Glimmer of Hope / A Glimmer of Hope, you'll have a near-endless supply of discard fodder. Once his stats are 5s or more across the board, you may not need to be committing your Glimmers anymore; repurposing them to cancel incoming damage/horror can be very worth it.
Short Supply and/or Lucid Dreaming can help you get all three Glimmers into rotation faster, but since it usually takes a while to power Calvin up anyway, you should have some time to draw into them with the likes of Take Heart, Self-Sacrifice, and friends.