Wirewood Symbiote

Return an Elf you control to its owner's hand: Untap target creature. Activate only once each turn.

Forest

{T}: Put a +1/+1 counter on target creature for each Elf you control.

{T}: Add {G} for each Elf on the battlefield.

Create a 1/1 green Elf Warrior creature token for each Elf you control.

{T}: Add {C}.
{G}, {T}: Untap target Elf.

Other Elf creatures you control get +1/+1.
{T}: Add {G} for each Elf you control.

Whenever another Elf you control enters, put a +1/+1 counter on Marwyn, the Nurturer.
{T}: Add an amount of {G} equal to Marwyn's power.