If you're playing Elden Ring Nightreign solo, every merchant carries a revive item, you can carry two at once, and there are more solo QoL changes coming next week

Duchess and Wylder in Nightreign.

Yesterday, FromSoftware put out an unexpected day one patch for Elden Ring Nightreign that already included balance changes for the roguelike soulslike. The patch notes were characteristically terse, but they've already overhauled the solo experience, and we can expect another patch next week with further adjustments.

But if you're playing Nightreign solo right now, here's the tldr: Most (all?) merchants now carry a Wending Grace item that revives you to full health when you die at a night boss. This is only in singleplayer, you can carry two at a time, and you should buy one whenever you see it.