The most thematic way to use them is to include one copy in your deck and trust in the Heart of the Cards to deliver it exactly when needed
These are borderline classic cards, and when they get new treatments its a nice chance for MTG fans to grab special versions of them and spice up their decks
P/T Number 218 Language English Legal Formats Commander, Legacy, Modern, Pioneer, Vintage Not Legal Formats Alchemy, Brawl, Competitive Brawl, Historic, Pauper, Standard, Timeless Rulings (9/15/2013) Numeric mana symbols (, , and so on) in mana costs of permanents you control don't count toward your devotion to any color
Note that this doesn't count as counters for other things like loyalty counters and charge counters on artifacts