How to be Knocked-Out in an HC Event:
-Be attacked for more damage than you have health for any HP level higher than 3 HP. See below for 3 HP or less.
--Additional: if your character is knocked out, they lose their transformation. It takes 5 MP to transform again. 
-Note: There are items in the Fate Exchange (the Crone's Blessing; the Crone's Nod) that can be used (either instantly or after battle) by the character or another party member to revive a character from being Knocked Out; otherwise characters will be relying on the Revive magical ability from another ally. 
-Time IRL will not revive a KO character. The only time a KO character will be revived with waiting would be if over 6 hours of in-game time has passed or it is the end of the Event and the Crone is involved. 
--I do not intend to change the time rule so long as player characters have the ability to reverse KO for a cost, as it brings another level of character interaction into play; the option to revive or not to revive (yeah, it is their character playing god) is an interesting consideration for character development, as are the consequences that are the reactions of other characters involved – not only the unconscious person, but other team members. The potential bonding or conflict caused by such decisions is welcome in an otherwise primarily characters-versus-environment setting.

How to die in an HC Event:
-Be attacked when you have less than 3 HP for greater than 3 points of damage. 
     If you had 4 or more HP and were struck by an attack for 5+ DMG, you will be reduced to zero and knocked out; 
     If you have 3 or less HP and are struck by an attack of 4+, your character can die. 
     If you are KO and are struck with an additional attack, your character can die.
--Additional: if your character is knocked out, they lose their transformation. It takes 5 MP to transform again. 
-Note: There is an item in the Fate Exchange for 100 points (the Crone's Stamp) that, when faced with the death-dealing blow, will teleport your character back to their home planet at the very last second, sparing them from death but ejecting them from the event.

What happens when your character dies in an HC Event:
When killed in the KO state, characters will die immediately if attacked while knocked out. If they have under 3 HP when attacked and killed, they can post a death post as their character is conscious and can react to their own death.

In the event of a character death in a HC event, the character cannot be involved in any future HC Event because in this timeline, they are dead. Similarly, if other characters who adhere to this universe set a roleplay after that HC event, time-wise, they can stipulate that 'dead' characters do not play as they have accepted that character's death into their history. This isn't a set-in-stone, no-exceptions rule that must be followed - it is optional for the storyline creator, but players of dead characters should not take offense to that character being excluded as the death was adopted into other characters' storylines and players are expected to adhere to character profile information in all non-AU storylines.

Why include Character Death as an option in Hardcore Events?
Character death is never a near certainty unless a character actively puts themselves into that situation. It either takes a lot of terrible choices or a lot of bad luck for a character to be Knocked Out, let alone die, as the characters are to be functioning as a team and, if relationships are fostered, willing to protect each other and help each other out. 

The chance of dying stresses the need of teamwork within the group, of forging relationship with between characters who would rush to a character’s aide or leap forward to protect them when put in a position wherein death is possible; as death would not come suddenly (though being knocked unconscious may), there will always be a possibility for a character’s friend or ally to step forward to save them before it's too late.  
 
As to why a player would risk a character they have put much time and effort into in a game wherein their character would die, I would return why not? No risk, no reward – no guts, no glory. With the statement above about how hard it actually is to get KO’d (let alone die), putting that on the table just ups the anti during battle sequences. 
 
And beyond that, what is the risk? If a player would rather not have their character play in these events where the character could die and the consequence would be that that character could no longer play in those events, you’re already “killing” your character without letting them go out with a bang or affect the lives of their teammates in their passing – they would simply fade away from the story, as opposed to living and fighting alongside them, making friends and deepening relationships, perhaps to eventually die dramatically and be remembered by these characters for events to come. If you’re going to go out, go out with a bang, rather than a whimper.