A Dion, Bahamut's Dominant Commander deck is a Knight Typal deck, meaning it's a deck that focuses primarily on one creature type, in this case, Knights
For the former, a +0/+1 boost is surprisingly impactful, putting your 1/1 Snake buddies out of range of ping effects, but the latter is where Sachis real power lies
Given the low cost and the trigger for a +1/+1 counter being quite generous, this has all the makings of a very dangerous early-game card that could contribute to quite a few quick wins if your opponent can't deal with it and remove it from the battlefield within one or two turns.
The effects aren't as amazing as the others, with Go-Shintai of Ancient Wars' direct damage and Go-Shintai of Shared Purpose's creature token creation being the two most worthwhile here
You must still follow any relevant timing rules for the permanent spell you cast from exile
Its so much of one, in fact, that, in hindsight, were staggered that this card wasnt expensive during pre-sale