Augury, reworked

By casting gem-inlaid sticks, rolling dragon bones, laying out ornate cards, or employing some other divining tool, you receive an omen from an otherworldly entity about the results of a specific course of action that you plan to take within the next 30 minutes. When you finish casting the spell, roll a number of D20s determined by the omen you received from the spell and record the corresponding number, you may only have one roll recorded by a casting of this spell at a time. Until your next long rest you can replace any attack roll, saving throw, or ability check made by you or a creature that you can see with one of these foretelling rolls. You must choose to do so before the roll, and you can replace a roll in this way only once per turn.

The DM chooses from the following possible omens:

• Weal, for good results roll two D20 and record the higher of the two. 
• Woe, for bad results roll two D20 and record the lower of the two. 
• Weal and Woe, for neither particularly good nor bad result roll one D20 and record your roll.  

The spell doesn't take into account any possible circumstances that might change the outcome, such as the casting of additional spells or the loss or gain of a companion.

If you cast the spell two or more times before completing your next long rest, there is a cumulative 25 percent chance for each casting after the first that you get a random reading. The DM makes this roll in secret.