You have not cast a creature spell using Karador this turn.
Coretapper does not have summoning sickness.
({2} magic symbol) each turn available.
Steps
Activate Coretapper's first ability by tapping it, putting a charge counter on Magistrate's Scepter.
Activate Coretapper's second ability by sacrificing it, putting two charge counters on Magistrate's Scepter.
Activate Magistrate's Scepter's second ability by tapping it and removing three charge counters from it, causing you to take an extra turn after this one.
Cast Coretapper from your graveyard by paying ({2} magic symbol) .