Luck sometimes follows you wherever you venture. When you finish a long rest, the GM rolls two 2d10s, keeping the results secret.
As a reaction, which you use when you make an attack roll, an ability check, or a saving throw you can call upon this luck to replace the roll with the highest of the results that the GM has. You can do so after the roll but before any effects of the roll occur. Each roll can be used only once.
When you finish a long rest, you lose any unused rolls.