Defending
When a PC or NPC applies a force against another character or entity with the objective of taking them out or disabling them, one side "attacks" and the other "defends". This can be a social encounter, a task to attempt to disable a device or obstacle, or a violent exchange.
The GM declares which Ability to use for the attacker and the defender.
Physical Combat
In melee combat, VIG is usually used to attack. For ranged attacks, PER is used.
To defend in combat, a character has two options: The most straightforward is DEX to attempt to dodge the attack. But they can also attempt to bear the brunt of damage and use VIG (that is, instead of dodging, you meet it head on). In that case, note that sometimes, even succeeding in your roll might mean taking at least 1❤️ anyway. It depends on fictional positioning (if you have armor or not, the type of damage, etc.). For instance, a blade against an armored character might not deal any damage when defending successfully with VIG, but falling rocks or the breath weapon of a dragon might still do 1❤️ if you just "tank" with VIG; even on a success.
Social Encounters
Two or more characters trying to outsmart each other, debate or make a point between them (or in front of an audience) also need to attack or defend. Usually the attacker uses CHA and the defender uses WIL, but in some cases, depending on the nature of the argument or the point risen, the GM might allow the use of INT or CHA to either attack or defend. ❤️and 💧are lost and gained as with any other conflict, in this case representing the composure and mental exertion of the participants.
Other cases
Normally, in any case or type of situation in which a character or entity is being affected with an intention of being taken out or disabled, the conflict rules can be applied and the effort and resistance can be abstracted with dealing and losing ❤️. The GM must apply common sense into which Abilities must be used to "attack" and "defend".