Plague of Khovyd

When Plague of Khorvyd enters the battlefield,
select target player. That player receives a
virus counter. At the beginning of each end step,
add +1 to virus counter.
When virus counter reaches 19, target player
loses the game. All creatures cast by infected
player have when combat damage is dealt, add a
+1 virus counter to opponent with all effects
of Plague of Khovyd.
These counters cannot be removed.