Each character has 10,000 health points in all standard versus game modes. In Story, CPU opponents will have less (sometimes more?) HP to compensate for the multiple spellcards as well as no player healing or card reshuffling between each CPU lifebar and player continue, respectively.
Defense Modifier Edit
at 100% health: 100% damage taken
at 50% health: 85% damage taken
at 0% health: 70% damage taken
Damage proration appears linear. So damage taken drops 0.3% for every 1% health you lose. This includes chip damage, however some sources of chip damage are so small that they round up in the favor of the attacker slightly.
Combo Modifier Edit
When a player performs a combo attack a HUD appears beneath their life bar listing the number of hits, the total damage, the rate, and the limit. In order to prevent combos from being too devastating a proration mechanic reduces the damage of each subsequent hit in a combo by a percentage. This percentage is listed as the 'Rate.' Starting with the second hit of a combo each subsequent hit will do reduced damage. This system rewards players with more damage for landing attacks without the guarantee of a combo, making the player decide if they are willing to sacrifice greater damage potential for guaranteed damage.