This should be another Number C92 not CXyz. Barian is a Special exemption as it's supposed to represent Don Thousand who didn't have an exclusive Number.
Also Nightmare Stomper, for the "While it has Xyz Materials" part he's using the wording on Tiras for that. Overall to me I think the effect is not bad but may be UP considering on how hard it will be to get Number C92 as a Material.
agreed, this is really difficult to bring out. first, you need to get Heart-eartH Dragon out, which is a task in itself considering how little there is for level 9s (although galaxy queen's light plus Shaddoll roots do mix well) then there is the task of bringing C92 out, which requires you to have either 4 level 10 monsters (which is near impossible unless you use a Metal reflect slime with GQL, or just simply use a Rank-Up on Heart-earth Dragon), then, because it is a rank 12, you HAVE to use Rank up magic Astral Force as the ONLY card to bring this beast out. That is near impossible to pull off in a duel. if someone did that, it must either be indestructable, Lock heavy, or an Instant win condition like Horakhty.
To make this card usable, here is my suggestions, either
A. make it Rank 11 instead of 12 so you can use other Rank up magics besides Astral Force
B. Have a condition similar to "If this card has "Number C92: Heart-eartH Chaos Dragon", "Number 53: Heart-eartH", and "Number 92: Heart-eartH Dragon" as Xyz Materials, You Win the duel
C. Modify the C92 effect to " Once per turn, you can detach one Xyz material from this card; negate the effects of all other face-up cards on the field. If you do, gain 800 life points and inflict 800 points of damage to your opponent for each card that is negated
D. Add "When this card attacks, effects cannot be activated in response. Any damage you would take from battle your opponent takes instead.
Just my thoughts on how to make the card more powerful considering its near impossible summoning.
P.S Love the Shinryu artwork you went with