Every 3 times you shuffle your deck, gain 2 Energy.
The Sundial gains 1 charge every time your discard pile is shuffled into your draw pile (including effects such as Deep Breath and Reboot), and charges are retained between combats. The Energy is granted immediately after the deck is shuffled the third time.
The Sundial is arguably one of the stronger uncommon relics; it's very powerful in many infinite damage combos. In addition, it is activated more often in thinner decks, similarly to The Abacus.
Sundial is an Uncommon Relic.