about the concept of HP, I think it's necessary to explain that it's just a very abstract concept——————it's just expressing how difficult it is to kill this guy, or how much damage this guy can withstand before it falls.that's why it's called Hit Points instead of anything else such as Life Points.
It does not mean that this character/creature will withstand the damage by their own meat after being hit by enemy attacks.
As humans, when a 1th warrior is hit by a giant's hammer, they immediately turn into minced meat, while a 20th Fighter and even a 20th Wizard should only take minor damage————Is the meat of a 20th Fighter and 20th Wizard completely different from that of a 1th Warrior? Does becoming a 20th character mean they have acquired Kryptonian bloodline?
No, the actually what happened is not like that. when a 1th warrior hitted by a giant's hammer, he is helpless and turns into a puddle of meat sauce.but the mighty and badass 20th characters are completely different.
when a 20th fighter hit by a giant's hammer, he can dodge at the last moment with his superb combat skills, only to be bounced away by the shockwave or break a few nails.
and for a 20th wizard,although he has no combat skills, when he is hit by a giant's hammer, a lot of shinny flare of defensive spells will immediately appear around his body, bouncing him away or offsetting most of the impact.
Similarly, when most humans are hit by a 5.45x39mm bullet, they will immediately down and die, even in the luckiest cases themstill would be amputated or get some permanent trauma. but if it were Rambo, the situation would be different. his keen senses and intuition were able to make him react at the last minute, suffering only the slightest damage, or simply because he was very lucky (otherwise he would have died long ago)————so he had much much more Hit points than normal soldiers.