At the beginning of combat on your turn, another target creature you control gains haste and gets +X/+X until end of turn, where X is that creature's power
I love the example thats given in the original
My gut says that this likely costs way too much to be worth it
Like most Magic: The Gathering cards, the value of Solemn Simulacrum depends on a few consistent factors: its rarity, the printing and finish (regular or foil), its physical condition, and the set it was printed in (Foundations)
Now, with the two Forgotten Realms sets and black-bordered UNFINITY cards to help build out a dice-heavy archetype, its only a matter of time until this card which many players already run casually to be officially sanctioned for use
You can see why this is a good fit