In the manga and anime, the field available for use in the Duelist Kingdom preliminaries when playing in forest regions. It powered up affected monsters ATK and DEF by 30%. Weevil Underwood used this to power up his Insect monsters against Yami Yugi.
In Yu-Gi-Oh! The Duelists of the Roses, this terrain can also be made by using the effects of "Arsenal Bug".