Nehtil, Endless Storm

{t}: Put a burst counter on Nehtil, Endless Storm.
{t}, Remove a burst counter from Nehtil, Endless Storm: Add {u} or {r} to your mana pool.
Sacrifice Nehtil, Endless Storm with seven burst counters on it: Search you library for an instant or sorcery card, reveal it and put it into your hand. Then take an extra turn after this one.