Dratini

Whenever you draw a card, remove all counters,
except charge counters from Dratini; then put
a charge counter on Dratini.
At the beginning of the End Phase, if Dratini has
three counters, you may sacrifice it. If you do,
search your hand and library for a card named
Dragonair, and place it in the battlefield.
Shuffle your library afterwards.