[quote=@Sublimation]
Ah things I would like to point out. Noble phantasms do consume mana. Nidhogg using one of such power and scale WILL drain his reserves. If he was a phantasmal species he would have EX ranked mana to balance this out, but I'm not sure we can classify Nidhogg as one. Medusa is classified as a demon, and so would Nidhogg considering how similar they are. The 666 Beast is also classified as a demon. Unfortunately, demons outside of True Demons lack the same stat capacity as phantasmal species do. However, Raijin has given Nidhogg prana burst(?) which is unique to phantasmal beasts, so I am thinking he has Nidhogg pinned as a phantasmal beast(???).


Also, being summoned in the Holy Grail War does limit heroes in stats. There is a limit to what the grail can summon, hence why Heracles doesnt move mountains and gouge out chasms with each and every attack. Hence why Karna doesn't punch people with enough force to "shake the entire universe"(Yes, this is what happened in the Mahabarata).
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Prana burst was suggested to me by someone else in the RP I originally made him for, on account of him being a dragon, and I think that he would technically count as a Divine Beast, plausibly, but he does have a down-grade, His more powerful curses will not be used very often, if at all, and it's why Nidhogg is best with a master that doesn't care for his eating of regular people. The amount of Prana that Thomas would have to give Beast in order to sustain his abilities would be quite a bit other wise, but as is, Nidhogg fuels the roots with those he kills.  An that will be his main way of fighting, besides his claws and use of prana burst.