Like most Magic: The Gathering cards, the value of Harmonic Sliver 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 (Time Spiral Remastered)
You cannot choose to have it enter the battlefield as a creature
In the Pokmon TCG, players use decks of these cards to battle each other, strategically deploying Pokmon, Trainer cards, and Energy cards to overcome their opponents
It allows you to grow your creatures to unlock board stalls, while enabling some very interesting synergies by dishing out creature abilities to your team
Carth the Lion
Offspring doesn't copy things like auras or equipment attached to the parent, though