This creature gets +1/+1 as long as you control an Island.
: Tap target creature.
"Thieves and squid squirm the same way when you capture them."
Illustrated by Mark Winters · Magic 2015 · #8
There are no rulings for Dauntless River Marshal.
As long as you control a Bird, this creature gets +2/+2 and has flying.
As long as you control a Griffin creature, this creature gets +3/+3 and has flying.
As long as this creature is untapped, green creatures you control get +1/+1.
As long as you control a Giant, this creature gets +1/+1 and has first strike.
This creature gets +1/+2 as long as you control a Forest.
Metalcraft — As long as you control three or more artifacts, this creature gets +2/+2 and has flying.