The goal of this conference is to survey how compact objects produce photons, neutrinos, and cosmic rays. The conference will focus on the physical conditions in magnetospheres, accretion flows, and jets of supermassive black holes and microquasars, as well as neutron star magnetospheres, pulsar wind nebulae, and pulsar halos. By bringing together observers of high-energy neutrinos, cosmic rays, and electromagnetic emission from radio wavelengths to ultrahigh energy gamma rays with theorists working on GRMHD, kinetic plasma physics, radiation transport, and particle acceleration, the conference will connect recent results from IceCube, HAWC, LHAASO, H.E.S.S., IXPE, and the Event Horizon Telescope with advances in theory and simulation. Particular attention will be given to identifying common mechanisms across compact object environments and clarifying how data can diagnose the engines of extreme particle acceleration.