Card (Marco) FOIL NNO DON
You can tap any three untapped artifacts and/or creatures you control, including Warden of the Inner Sky itself and other creatures you haven't controlled continuously since the beginning of your most recent turn, to pay the cost of Warden of the Inner Sky's activated ability
For an incredibly mana-cheap cost of 1G (one generic mana and one green), Heroic Intervention grants all of your permanents Hexproof and Indestructible for the turn
The payoff is decent but in cube I cannot advocate running this over Journey even if you are trying to up the one drop removal options
The turn after a Wheel usually means a dozen or more points of damage for an unlucky opponent via Lightning Bolt, Goblin Grenade, Ball Lightning, Fireblast, Chain Lightning, and other cheap burn effects
Whispers of the Muse (Draw) 39