Relic of the Precursors

Relic of the Precursors enters the battlefield with
5 time counters on it.
Whenever an opponent casts a spell remove a
time counter from Relic of the Precursors.
{5},{t}: Destroy target nonland permanent with converted mana cost 5 or less. Activate this ability only if Relic of the Precursors has no time counters on it.