Marvel vs Capcom 3/Game Elements/Red Health
Recovering Red Health
You'll notice that during the course of the game, as characters take damage, a portion of any character's Life Meter can be solid red instead of being filled up or empty. This is very important because what portion of your Life Meter is red can be recovered back into health again. And the main way to recover health is to be tagged out and be in either of the Assist Character roles. As long as the character remains as an Assist Character, their Red Health will recover at a steady pace until all of the Red Health has been recovered. However, if the character is called during a Cross-Over Assist and is struck, the Red Health will stop recovering for a short period of time. After that time, it'll resume its normal recovering behavior.
Point Characters do actually possess a way to recover their Red Health: X-Factor. As soon as you activate X-Factor, one of the benefits is that you will begin to recover whatever Red Health you have as the Point Character (the assist character regenerate red health at an accelerated rate as well). If you get hit or Block any attacks, the recovery will stop for a bit but eventually will commence again after a short period of time. Outside of X-Factor, two characters posses an extra way to recover Red Health as the point character. Dante can recover Red Health after activating the Devil Trigger. And Phoenix has the Healing Field Hyper Combo, which will recover the Red Health very rapidly so long as the opponent is inside the field.
Gaining Red Health
So how does one end up with Red Health in the first place? There are two ways, one as a Point Character and one as an Assist Character. As a Point Character, any move that does damage to you will always leave some Red Health behind. The amount of Red Health you have is always 50% of the damage of the attack that hit you. So if a move does 50,000 damage, 25,000 points will become permanent damage, represented by the now empty portions of your Life Meter, and the other 25,000 points will become Red Health at the end of your regular health.
This also applies to Chip Damage as well. Any move that will do a small amount of damage to you even if you block them (Special Moves, Hyper Combos, etc.), will always cause equal permanent damage and Red Health. Also, if you already had some Red Health, all additional Red Health will just be added to it. So as you get beat up more and more, the chunk of Red Health grows larger and larger.
The second way you can gain Red Health is as an Assist Character. When you are called into battle as an Assist, you can be hit and take damage. The bad news is that Assist Characters take 50% more damage from hits than if they were the Point Character, so it takes less to K.O. an Assist. The good news, however, is that Assist Characters only take damage in the form of Red Health! So even if there was a move that would take off 95% of health off of an Assist Character, all 95% of that lost health would be in the form of Red Health that can be healed after some time.
Losing Red Health
If at any point in time you tag out your Point Character for an Assist Character using a Cross-Over Attack or a Cross-Over Counter, the Assist Character, when becoming the Point Character, will lose all of their Red Health! This happens, as well, to the incoming character if the Point Character is Snapped Out by the opponent or if the original Point Character was K.O.'ed. Obviously, losing that Red Health means they will never be able to regain that health ever again.
This is what makes the alternate methods of character switching so important. Aerial Exchange combos and Delayed Hyper Combos should become your preferred method of changing characters because, in both of those cases, the incoming character retains all of their Red Health! Which means if they somehow avoid a lot of damage and you tag them back out later on, whatever Red Health they had before can still be healed, even though they became a Point Character at one point.
Red Health Vs. Actual Health
And remember: Red Health technically doesn't exist. Even if you have the largest chunk of Red Health left, as soon as you lose the last bit of your regular health, you are defeated. So in the example above, even if your Assist Character has 95% of their Life Meter as Red Health, if you call in that Assist and they get hit by an attack that drains the last of their 5% Life Meter, they will be defeated anyhow. Red Health is only there to indicate how much life you can recover.