Good examples would be Salamangreat Violet Chimera, which gets a powerful ability if you use a different Salamangreat Violet Chimera as material, or Dual Avatar - Manifested A-Un, which gets a range of different powerful effects for summoning with different Fusion monsters
You can reach out to us at @MTG_Arena using the hashtag #MTGAlchemy, and we'll include any additional questions and answers in next week's blog.
However, if the passive ability turns out to be popular, the price is very likely to spike
2 Bello, Bard Of The Brambles The Commander Has Come Out To Play With a deck filled with tons of unique cards, Bello, Bard of the Brambles still stands out
It is a Structure Deck for Yu-GI-Oh
That said, there is another, less obvious, candidate that can be easy to forget about