The Demon Core

At the beginning of each end step, each player gets a rad counter.
Tickling the Dragon's Tail —{7}, {t}: Exile all creatures, graveyards, and artifacts. Roll a d20. Target player gets X rad counters based on the result.
1-15 | X is number of cards that left the battlefield this turn.
16-19 | X is the number of creatures in exile.
20 | Target player gets 1,000 rad counters.