When you dream, you glimpse your immediate future. Whenever you complete a long rest, roll 1d4. Twice per long rest, add or subtract this number to any d20 roll you make. This alters the actual number on the d20 before any modifiers. So if the d4 roll was 1 then a d20 roll of 19 can become a natural 20. In addition, if you rolled a 4 on the d4 then you may use this number three times per day.