In this talk, I'll review the construction of gravitational constraints and of the corresponding phase space along generalized Horizons.

I will focus my expose on the study of the Raychauduri Constraint and its quantization, which describes the dynamics of quantum null rays. I will present a detailed construction of the null Ray phase space and the localized gauge-invariant observables.

Such a construction requires the introduction of a preferred time frame called the dressing time, which includes edge modes that allow localization along a null ray interval. Gauge-invariant observables are then obtained by dressing the fields with the dressing time.

We will see how the edge mode symplectic structure can be understood in terms of the integration of degrees of freedom complementary to

chosen region and how the gauge invariant observables include the covariant area element as a generator of reorientation of the frame. Overall the dressing time this provides a gravitational description of a quantum reference frame.

Finally, we will describe how the quantization procedure can be encoded through an effective deformation of the gravitational phase space labelled by a central charge.

If time permits, I'll comment on the role the central charge plays in resolving the fundamental problem of time in quantum gravity and on some new results concerning the quantization of field theoretical reference frames.