In the revised Vivid system, Aces are used to save the character from damage. Vivid’s default assumption is that any defeat spells the end for a character; but if you have an Ace to use, you can stay in the fight by spending points from it.
There are by default three Aces, to which beginning characters can assign 0-6 points: Guts, Wits, and Luck. Armor also acts as an Ace, if you have it. To see how this works, put it this way: Conan the Cimmerian survives his battles because of Guts, D’Artagnan because of Wits, and Bilbo Baggins because of sheer Luck.
In Hari Ragat, though, there is only one Ace – Bala, or spiritual power. Every hero must quest to increase his Bala, and there are taboos to keep in order to maintain current levels.
Aces are refreshed by indulging in some activity relevant to the nature of the Ace. Guts for example is recharged by carousing or by re-establishing ties with your source of inner strength – it could be religious for a cleric, a beloved for a knight, etc. etc. Wits is refreshed by indulging in something intellectually stimulating – a game of chess, a night in a salon gathering, reading, etc. etc.
Luck has the broadest application among the Aces, so it’s also the hardest to refresh: to refresh Luck, you must volunteer a mishap to happen to your character! The mishap must be one that actually complicates the adventure, say by introducing new enemies or getting the party sidetracked. (Yes, Lucky characters are meant to be annoying!)