Forge bellows

The forge bellows is used as an upgrade for the forge. It is one of the two upgrades to the forge that does not use metal ingots, and can thus be taken through a portal. (The other is the grinding wheel.) Also, unlike the other upgrades which can be placed anywhere and provides buffs within range, this upgrade building's placement is only valid connected to the forge.
fr:Soufflet de forge
ru:Кузнечные меха