Fate's Hand

(as always with homebrew content, these mechanics are subject to re-balancing if necessary)
This artifact of Istus resembles a silver hand with all five fingers facing away from the palm, as if grasping something. Each finger features a small hourglass, each housing a different power. No matter how the hand is turned, the golden sand within each hourglass remains stationary until its associated power is used. The sand normally rests on the "palm" side of the finger, but when that finger's power is used the sand flows towards the fingertip. At dawn all sand is drawn back towards the palm, allowing expended powers to be used again.
Each power grants the wielder some amount of knowledge or control over fate. However, fate is resistant to change. Each time a power is used there is a chance that fate will fight back in a manner determined by the DM. Powers with some tangible effect might fail or have unexpected side effects. Predictions of the future might be incorrect or presented with misleading wording.
The odds of this happening are determined by the number of powers expended, according to the following table. The DM makes this roll in secret:

1st power	0%
2nd power	15%
3rd power	30%
4th power	60%
5th power	90%

Read Fate (Thumb)
As an action, choose a creature you can see within 60 feet of you. If the target is a hand of fate, you learn their title. Additionally, you can choose to receive a vision regarding the shape of the target's fate. You can ask a specific question or simply receive a general reading, but in either case the vision takes one minute and is usually vague and mired in symbolism. Sometimes the vision describes the target's past and other times their future. Predictions of the future are not infallible, but are very likely to come true if a hand does not intervene. If the target is not a hand, then your action is still consumed but the power is not expended.
Bestow Good Fortune (index finger)
When a creature you can see within 30 feet makes any d20 roll, you allow them to roll a second time and use either result. If the initial check had advantage or disadvantage, the target may only re-roll one die. This power must be used after the roll is made but before the DM announces the results.
Bestow Ill Fortune (middle finger)
When a creature you can see within 30 feet succeeds a saving throw, you may use your reaction to cause that creature to fail instead. If the target has some means of automatically succeding a save (such as legendary resistance), it can still use that ability to protect itself.
Acceleration (ring finger).
As a bonus action you slow down time, gaining an additional action on your turn and doubling your speed until the end of the turn.
Reactive Acceleration (pinky finger)
As a reaction when a creature you can see within 30 feet of you takes damage, that creature gains an additional action if it is the creature's turn, or can take an action immediately even though it isn't the creature's turn.