To restore the day-night balance, the Celestus mechanism's Sungold Lock must be reunited with its long-lost key.

Moonsilver Key

{1}, {T}, Sacrifice Moonsilver Key: Search your library for an artifact card with a mana ability or a basic land card, reveal it, put it into your hand, then shuffle.

Innistrad: Double Feature

Innistrad: Midnight Hunt

Most mana abilities found on artifacts are activated mana abilities. An activated mana ability is an activated ability that could produce mana as it resolves, does not require a target, and isn't a loyalty ability.

Some artifacts, such as Gauntlet of Power, have triggered mana abilities. A triggered mana ability is a triggered ability that could produce mana as it resolves, triggers on the resolution of an activated mana ability or on mana being added, and doesn't require a target.