Yannik, Scavenging Sentinel | Fiend Hunter | Changeling Hero

Cards

Fiend Hunter in hand.
Changeling Hero on the battlefield.
Yannik in hand or in the command zone.
({3} magic symbol) ({G} magic symbol) ({W} magic symbol) ({W} magic symbol) ({W} magic symbol) plus enough mana to pay for commander tax, if applicable available.

Cast
Yannik by paying ({2} magic symbol) ({G} magic symbol) ({W} magic symbol) and commander tax, if applicable.
Yannik enters the battlefield, exiling
Changeling Hero and distributing a number of +1/+1 counters equal to
Changeling Hero's power among creatures you control.
The creature that was championed by
Changeling Hero returns to the battlefield from exile.
Cast
Fiend Hunter by paying ({1} magic symbol) ({W} magic symbol) ({W} magic symbol) .
Fiend Hunter enters the battlefield, exiling
Yannik.
Changeling Hero returns to the battlefield from exile, championing
Fiend Hunter.
Fiend Hunter leaves the battlefield, returning
Yannik to the battlefield from exile.
Yannik enters the battlefield, exiling
Changeling Hero and distributing a number of +1/+1 counters equal to
Changeling Hero's power among creatures you control.
Changeling Hero leaves the battlefield, returning
Fiend Hunter to the battlefield from exile.
Repeat from step 5.