Flagstone Spy

Flagstone Spy
UnitSoldierCost: 3ATK: 3 HP: 3
Invisible (To opponents without a detector, he's untargetable, unattackable, and can sneak past patrollers. While patrolling, he's attackable.)
Whenever Flagstone Spy deals combat damage to a building, look at that player's hand and steal ① from them.
BluePeace Tech II

Card-Specific Rulings
His ability that steals gold can't steal any against an opponent that doesn't have any gold. — 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