Fox's Den School

Fox's Den School
Legendary BuildingCost: 4ATK: HP: 4
Your Ninjas and Cute Animals are invisible.
②, ⤵ → One of your units becomes a Ninja (in addition to its other types.)
WhiteNinjutsu Tech II

Card-Specific Rulings
A unit that becomes a Ninja this way stays a Ninja until it leaves play. Even if Fox's Den School leaves play, your unit remains a Ninja. — Sirlin
Invisible Rulings
"Sneaking past" means you can ignore patrollers when attacking and attack anything you want. You can also attack the patrollers if you prefer. — Sirlin
When something invisible attacks an enemy unit or hero, that enemy unit or hero DOES deal its combat damage back as usual. — Sirlin
If an opponent has the Tower add-on and their tower has already used its once-per-turn detect on something, then you attack with something invisible, the Tower will not deal its damage to your invisible thing. It would if it's once-per-turn detect hadn't been used, but it can only damage things it can see. — Sirlin
You can [target] your own invisible things whether you have a detector or not. — Sirlin