SmB6, a long-known mixed-valence material, has been proposed as the first topological Kondo insulator. Early neutron scattering experiments revealed a 14 meV resonant mode at low temperatures. The mode is resolution-limited and coherent, with < 2 meV dispersion repeating outside the first Brillouin zone. It shows a clear and dramatic decrease in lifetime by doping of rare-earths, indicating involvement of the Sm site, yet it has an anomalously sharp magnetic form factor which necessitates a wave function decidedly more extended than 4f electrons (such as from Sm3+). Using ultra-high field magnet neutron scattering, we propose to determine the spin-space degeneracy of the exciton, which is ultimately closes to form the novel topological surface states in SmB6.