Colloidal spheres have proved a convenient model system to study crystallization mechanisms, allowing for example to track individual particles, dislocations or grain boundaries, a complicated task for atomic systems. The theoretical framework of dissipative systems is open, and using active colloids -which continuously consume energy- allows us to probe dynamics out of traditional scope of equilibrium physics. We experimentally study the dynamics of a dense monolayer of passive colloids, relaxing after being quenched in a polycrystalline state with domains of mismatching orientations. A small fraction of active intruders navigates within the crystal. We study the evolution of the polycrystalline pattern, ensuing from the interplay between the self-propulsion of active particles and the rearrangement of passive colloids induced by this internal activity. The intruders are shown to massively speed up coarsening processes leading to an ordered phase, with a reorganization dynamic dependent upon the number of intruder and their activity. Our findings uncover the role of active dopants to boost the relaxation of a system and show their potential to control the properties of matter microscopically and in real time.