There are pretty much 4 of them that I will eventually talk about over the course of Decks 1,2 &3, and each has their specific place to shine
For those not in the know, these two siblings have been integral to countless moments in Magics story, and are some of the most mythic of characters in the story, albeit not quite as popular as the likes of Nicol Bolas
The change in power level between four and five drops may not be the steepest change but it is one of the more significant ones as it falls within the realms of the cards you can include without ruining your curve or consistency
If you can take two thirds of the best uses for a card away along with half its overall utility and still have a playable card then it suggests a lot about the power of that card in the first place
Finally, its worth pointing out that Jennifer Walters is a second Voice of Victory legal in Standard, and another of this effect legal in Canlander, which is making her quite the attractive acquisition
An Aura put onto the battlefield this way doesn't target anything (so it could be attached to an opponent's permanent with hexproof, for example), but the Aura's enchant ability restricts what it can be attached to