History of Mote

Motes are the currency of Gambit: glowing triangular drops of concentrated Darkness (see also Mote of Dark) that defeated enemies leave behind. Players collect them by running over them, with tougher enemies dropping more, and carry up to 15 at a time.

Banking

Motes are deposited at a bank. Banking a batch sends a Blocker to the opposing team's bank; two or more blockers begin draining that bank. Banking enough motes (100 in the Destiny 2 Wiki's description) summons the Primeval. Every 25 motes banked opens an Invasion portal letting one player become an Invader; an invading Guardian killed yields motes too.

Risk

Dying while carrying motes loses them. Sources disagree on details: the Destiny 2 Wiki says the player drops half (rounded up), while another community page says the whole stack is lost and the team's progress drops double. The blocker types per batch size also differ between sources (for example the Taken Knight versus Phalanx tiers), so verify in game. Neither source covered Gambit Prime differences.