Then if they kill it, your opponent has to attack you and take damage
The card has a combo shift cost of four ink and comes with The Power of Friendship ability, which states that when this character is banished, if any of the cards that were under them are character cards, you may play those characters from your discard pile for free
Holding cards for coordinated plays later, setting up powerful Songs, knowing when to sacrifice characters to banish an opponent, anticipating the play your opponent is setting up based on their deck composition
There is an argument to be made about the Final Aeon possession also being part of this mechanic, but I am not really so sure
In some respects, Emerald and Ruby falls somewhere between the aggression of Amber and Amethyst and the controlled ramping of Sapphire and Steel