A players team cannot contain two Pokmon of the same species, that is, with the same National Pokdex number (for example, Heat Rotom and Wash Rotom are not allowed, since both are still Rotom)
And then she died, and there was a Memorial in the next set that gave your creatures all of the abilities of the first Akroma
So, just looking at this as a four mana 4/4 that can take a turn off to dig for an Equipment
This can turn your moderately concerning battlefield into something thats immediately terrifying for your opponents to deal with
In Midnight Hunt , Wizards gave us two such mechanics: Daybound/Nightbound and Disturb
The fact that he pushes out damage to all of your opponents at once is what makes Hallar even vaguely playable in today's EDH