If a card copied by the token had any "when [this permanent] enters" abilities, the token also has those abilities, and they'll trigger when it's created
Its also a boast ability which offers extra merit when activated immediately before blockers, allowing the Valkyrie to brush aside potential flying walls like Dream Trawler unless theyre accompanied by extra sacrifice fodder
I what card shops use so I know that these were what I was predominately looking at, but thats enough of that
With blue being necessary, the pairing has typically been between white and/or black
For just 1 white mana at instant speed, you get to search your library for any artifact (or enchantment), reveal it, and place it on top of your deck
It is a strategy that is currently unchallenged