A variable axis turbine may include multiple nested rotatable rotor assemblies. The turbine may be self-starting in slow fluid conditions while simultaneously self-limiting in fast fluid conditions. The turbine may provide omni-directional energy recovery and be self-balancing. The nested rotatable rotor assemblies may be configured to rotate independently of each other, but along the same rotational axis. Each outer nested rotor blade set may direct fluid onto the inner rotor blade sets in an aerodynamically beneficial manner. Each rotor blade set may be interconnected with a rotating generator hub that encloses a rotating generator element that rotates along with a corresponding rotor blade set for electric power generation. The blades may be “smart blades” that are sufficiently flexible to be self-configuring during rotation and soft enough to partially absorb sound. The blades may have a variable hardness and a two or more dimensional twist.