Alarum

Paladins use this spell to communicate with others of their order, an incredibly valuable, if simple tool. When you cast this spell, holding the candle above your head as you chant, you prime yourself with the alarum, which will activate under certain conditions.

When one of these conditions is met, a blazing ball of light appears in the sky above you, visible out to a mile in every direction; even if you are underground or below water, the alarum will shine in the sky no matter the distance, though visibility conditions may make it difficult to see. The color of the light indicates the level of danger you are in; the ball appears red if you faint in battle, orange if you faint for any other reason, yellow if you suffer penalties relating to exposure, hunger, or thirst, or blue if you trigger it voluntarily (as an action). The alarum. Once activated, lasts for a full day, or until you end it as an action.  If you die, the alarum's color changes to white.

A paladin of 10th level or higher who shares your deity or order of knights, has a 10% chance to sense this over any distance, regardless of sight. This chance increases by 10% for each level in paladin beyond 10th, with paladins of 19th level or higher being able to sense it without fail.