[Ashterot the Grimmsnarl] and [Nyrgal the Ditto] are both cut from the same bombaclaat.

Nyrgal's assholery stems from trust issues and a general disdain for humanity due to his experiences in the custody of Pokemon Hunters - who abused him in a multitude of ways, and later by mad scientists - who saw him as nothing but a test subject, which would later result in his then-unstable physiology and developing his Social Darwinian mindset - partly believing that his capture occurred because he was weak and strength was a necessity for survival. For any type of training to occur, Elio had to prove his own power and demeanor to Nyrgal on multiple occasions for the Pokemon to slowly warm up and willingly follow his commands.

Though, fortunately, Elio had a head start in gaining Nyrgal's trust after the latter witnessed Elio's one-man campaign against the same group of Hunters who once tormented him - even going as far as to offer the Ditto a chance at vengeance, which he gleefully took. In fact, their bond developed by leaps and bounds whenever the two eliminated Pokemon Hunters or humiliated arrogant individuals who abused others through their position - with Nyrgal gaining satisfaction out of destroying those in power rather than helping those weaker than him. Regardless, even when the two became close enough for Nyrgal to follow Elio's instruction, he was quite selective about what he learned and who his training partners were - preferring to follow his own path to indomitable strength and wanting to cause as much mischief as possible, staying true to his <Impish> nature.

On the other hand, Ashterot's assholery stems from his (well-founded) inflated ego - which frequently clashes with his oddly eloquent mannerism yet complimented his barbaric fighting style; he's self-sustaining and really didn't need a trainer to draw out his power. In fact, Elio considers himself to be Ashterot's trainer by technicality due to meeting the Nigredo standards, the latter finding him rather interesting via sensing Elio's cultivated power and becoming well-acquainted with the former's desire for freedom, and later being impressed with Elio's lavishness stemming from his self-cultivated financial status - drawing out his own desire to enjoy the finer things life has to offer.

While Ashterot's Nigredo strain is one of the few that's highly concentrated - thus explaining his robustness, imposing size, inverted color scheme, advanced intellect, other notable biological features (i.e. his hair follicles, fangs, muscle density, etc.), and extensively heightened development rate, after much observation and interaction - usually with the two being at odds with each other to certain degrees, Elio's decided that training him would be fruitless as the Ogre would produce astounding results if left to his own devices - something that's proven time and time again, with Ashterot frequently performing feats outclassing even the most well-trained veteran Pokemon after undergoing hours of self-discipline, replication, and extreme physical training. Such drastic leaps in power also stem from his humiliating experiences dealing with [Heim the Alolan-Ninetales], [Rowen the Metagross], [Lucifel the Wiseraph] and [Orochi the Serperior] - severely crushing pride while, in turn, spurring his drive to surpass and humiliate them to establish his "dominance".