Hey @Jose_Carlos_Poeiras and welcome to the forums! 
Great work on those dragons. To get some interaction, I’d take a look at the Attach Constraint. It will enable you to dynamically parent the foot of one dragon to the foot of another, and control the intensity with which they are attached along with the distance and orientation they should have relative each other.
For example, here, the feet are dynamically attached to each other, and later un-attached by animating Stiffness to 0.
Here’s how to do it.
- Select child
- Select parent
- Ragdoll → Constraint → Attach
- Move attach constraint to where on the parent you want the child to be
Per default, the Attach Constraint will mimic the distance and orientation your controls have at the start frame. If you 0-out the values, it will be as if you parented the control to another control, and zeroed out its channels. It would go to the same position and orientation as the parent.
In this case, I want foot A to be close to foot B, and so I zero it out, and then turn it up-side down such that their soles touch.
This is the same technique Jason was using here:
Let me know how it goes, looking forward to seeing how it turns out!