Opponents collectively control at least nine creatures.
You have at least seven cards in your graveyard and/or in exile that are instants, sorceries or have an Adventure.
Steps
Activate
Gwenna by tapping it, adding ({G} magic symbol) ({G} magic symbol) that can only be spent to cast creature spells or to activate abilities of creatures.
Cast
Primeval Protector by paying at most ({1} magic symbol) ({G} magic symbol) .
Brinelin and
Gwenna trigger.
Resolve the
Brinelin trigger, returning
Sailors' Bane from the battlefield to your hand.
Resolve the
Gwenna trigger, putting a +1/+1 counter on it and untapping it.
When
Primeval Protector enters, it triggers, putting a +1/+1 counter on each other creature you control.
Activate
Gwenna by tapping it, adding ({U} magic symbol) ({U} magic symbol) that can only be spent to cast creature spells or to activate abilities of creatures.