Back to the Keyword:
I thought about the Keyword and wanted to make it more individual:
Basic Gain: 16, Bonus Gain: 4, Side-Effect (Mana-Flames): Convert an amount of Enemy Gems equal to the Rarity of last played Card (C: 2, U: 4, R:7) into attack.
Basic Gain: 5, Bonus gain: 5, Side-Effect (Hell's Escape): Next Card received will be last Card played. Add Gems equal to the Rarity of last played Card (C:3, U:6, R: 12)
If you got a "Hell's Portal" in your Hand while playing a Demon Card, and if #Gems>13, replace one "Hell's Portal" on your Hand with a Demon Card of the Higher Rarity and reduce your Gems by 13.
If last Card played while triggering this effect is rare: