Tranquility is a Open Hand Monk feature gained at level 11 in D&D 5e. Beginning at 11th level, you can enter a special meditation that surrounds you with an aura of peace.
Beginning at 11th level, you can enter a special meditation that surrounds you with an aura of peace. At the end of a long rest, you gain the effect of a sanctuary spell that lasts until the start of your next long rest (the spell can end early as normal). The saving throw DC for the spell equals 8 + your Wisdom modifier + your proficiency bonus.