(2020-11-10) Although the ninjutsu ability has the creature enter the battlefield attacking, it was never declared as an attacking creature (for the purposes of abilities that trigger whenever a creature attacks, for example)
Ghostfire Slice TheChirurgeon: This seems like a sweet way to get 4 damage for R in Commander
More than just allowing lands to tap for any color, Wrenn and Realmbreaker also effectively protects themselves, which is always a potent ability
All in all, I'm not sure the juice is worth the squeeze here, at least in this case
Keep in mind, when you ready Aurora Waking Beauty through her ability, you cant Quest or Challenge with her, but you can Sing, so potentially, you can play two 5-cost Songs in one turn
Kros deals out shield counters (defense contractor), but there are other options