An opponent cannot block and kill creatures you control.
You have at least six experience counters.
Steps
Declare
Otharri and
Hellkite Charger as attackers, triggering their abilities.
Resolve the
Otharri trigger, causing you to get an experience counter and create at least seven 2/2 Rebel creature tokens that are tapped and attacking.
Activate
Phyrexian Altar seven times by sacrificing seven Rebels, adding ({5} magic symbol) ({R} magic symbol) ({R} magic symbol) .
Resolve the
Hellkite Charger trigger, causing you to pay ({5} magic symbol) ({R} magic symbol) ({R} magic symbol) to untap all attacking creatures you control and get an additional combat phase after this one.