Examples of valuable modern cards: Ragavan, Nimble Pilferer The One Ring (Special versions) Sheoldred, the Apocalypse Esper Sentinel Force of Negation (foils or premium prints) Why these cards hold value: Strong Commander demand Competitive Modern play Limited print variants Foil and showcase versions These cards can range from 20 to 300 depending on version
Abzan Advantage | Illustration by Winona Nelson Whenever the bolster X action happens, you put X +1/+1 counters on your creature with the least toughness
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Totem armor (If enchanted creature would be destroyed, instead remove all damage from it and destroy this Aura.), or one of the Ordeals from Theros, or
Reach doesnt apply when a creature is attacking
Next I would consider stuff like Shamanic Revelation, Collective Unconscious, Freyalise, Llanowar's Fury, or maybe Inspiring Call if you'll be distributing enough +1/+1 counters to creatures