i aleays though of It as he was just badly or mortally injured fighting 666 because trihexa is the strongest being in pure power,so in the process of sealing It he wouldn't escape without injuries, mainly because he was fighting a stronger being and it's not like he can put such at avance seal in a second, and even then he kill all the original satans and was able to hide his death to all other pantheons at the moment, with only the biblical higher ups knowing.

he also have levels, this meant that he can evolve too, so this is basically the equal to goburou gluttony ability.

now, It came to my mind something like the ability to apply his catalyst with poison to make things like a fire with a poison that buens you, the ice one Freeze you, the electric is a super paralitic poison, earth one petrify you, water is regular liquid poison but a very strong one and the Air one is a invisible gaseous lethal poison that make his alchemy extra dangerous, and maybe make that the hydra learn a element for head with the poisonous versiones that i put above, that let the hydra with three extra heads and i can think of one being light because all the light weak races that are in dxd and maybe shadow for other one, with the poisonous version things that i can't think of for now and the extra final head i don't think of a obvious one, there are so many elements to choose.

now he need to make a poison catalyst in base of his hydra and then help his hydra to become a true Nine headed poison dragon too.

i think that azazel just put all his job in them and he go to his sacred gear research and doing things that cath his interest.

i wasn't saying that humans can't learn, but that only youkais had a innate talent to It that make It something they can learn without problem, especially nekoshou, other races had all had almost nothing in senjutsu and that make It very hard to learn, you need a great teacher or go Sairaorg style and grind until awakened it

any race outside youkai aren't talented in senjutsu, and i was using Sairaorg as a example that If you break your limits of your body you can naturally learn touki, but more avance uses of senjutsu that can cause the corruption Will need him learning from someone with experience in It.

the first horseman is change between plague and conquest a lot in media, but If you go to the original conquest is the correct one but plague is the most popular one in this days

and the overuse is only If you use It a Lot in a Sort periodo of time.

is busted as hell, revive the dead, eliminate racial weakness and more, the only side efecto is that is strained the user a lot so If you overused too much It you can kill or cripple you, but this limit increase with the streght of the user, and all this in base form without balance breaker If i don't remember bad

you are right

It is never confirm whre hashirama Sage mode comes from, it's a mistery even now but people tipically default It to the slug because tsunade is his grandaughter.

juggernaut Drive go brrrrrrrrr