(Equipment, Auras you control, and counters are modifications.) The value of X needs to be determined both when the ability triggers (so you can choose a target) and again when the ability resolves (to check if that target is still legal)
Sazh's Chocobo [FINAL FANTASY Promos] Set: FINAL FANTASY Promos Type: Creature Bird Rarity: Uncommon Cost: ...
For each instant or sorcery with converted mana cost X or less among them, you may cast that card without paying its mana cost
Since silver-border cards arent legal in sanctioned play, they work best in casual Cubes or Rule-0d Commander games, and Ill rank them as such, with an eye towards fun and intrigue over raw power
Hylda of the Icy Crown (WOE-206) - Wilds of Eldraine Hylda of the Icy Crown (WOE-206) - Wilds of Eldraine Wizards of the Coast This item is like new, pulled from a sealed pack
It's good to be aware of these archetypes because they sometimes come up in Limited, like the Lost in the Woods "combo" in Dark Ascension Limited, or making your own surprising imitation of a Fog deck by just drafting a pile of removal and no good win conditions