Mark of Sakiko generates green mana based on power when you attack
Effects like Duress specifically interact with cards in your hand, and thats the only zone the game recognizes for discarding
Each character has a Strength value (how much damage they do in challenges), a Willpower value (how much damage they can take before being discarded), and a Lore value (how many points they give you when they quest)
Given that you'll already be dealing with your graveyard and sacrificing with black cards anyhow, it's not hard to get plenty of value out of Moonshadow's single mana cost, with menace being a little added insurance to make sure it doesn't get blocked too easily after you do
If all players can't agree if the card qualifies, you may ask an outside person for a final determination
Chain Assassination + Distract the Guards + Eagle Vision + Petty Larceny + Restart Sequence Each of these cards, if you can get them down for the 2-mana freerunning cost, is way above rate