Bed of Spikes

Bed of Spikes is a magic item (wondrous item) of rare rarity.

This wide, wooden plank holds hundreds of two-inch long needle-like spikes. When you finish a long rest on the bed, you have resistance to piercing damage and advantage on Constitution saving throws to maintain your concentration on spells you cast for 8 hours or until you finish a short or long rest. Once used, the bed can't be used again until the next dusk.