Tide Stones are named as much for their appearance as their effects. They bear a resemblance to sapphires, although they are dar darker and glow softly, evoking images of waves rolling in upon a beach. They weigh significantly more than they seem like they should.
These stones have the ability to turn the tide of a dire situation--for better or worse.
Once per day, a Tide Stone can be used to force a critical result during an ability check or attack roll. When the D20 is rolled, anything from 1-10 counts instead as a natural 1 and anything from 11-20 instead counts as a natural 20. Ability modifiers are ignored for this roll.