  Motivated by the recent detection of ultra-long period radio transients, we
investigate new models of coherent radio emission via low-altitude
electron-positron pair production in neutron stars beyond rotationally-powered
curvature radiation deathlines. We find that plastic motion (akin to
'continental drift') and qualitatively similar thermoelectric action by
temperature gradients in the crusts of slowly rotating, highly magnetized
neutron stars could impart mild local magnetospheric twists. Regardless of
which mechanism drives twists, we find that particle acceleration initiates
pair cascades across charge-starved gaps above a mild critical twist. Cascades
are initiated via resonant inverse-Compton scattered photons or curvature
radiation, and may produce broadband coherent radio emission. We compute the
pair luminosity (maximum allowed radio luminosity) for these two channels, and
derive deathlines and 'active zones' in $P-\dot{P}$ space from a variety of
considerations. We find these twist-initiated pair cascades only occur for
magnetar-like field strengths $B \gtrsim 10^{14}$ G and long periods: $P_{\rm
RICS} \gtrsim 120 \; (T/10^{6.5} {\rm K})^{-5} \, {\rm sec}$ and $P_{\rm curv}
\gtrsim 150 \; ({\rm v_{\rm pl}}/10^{3} {\, \rm cm \, yr^{-1}})^{-7/6} \, {\rm
sec}$. Using a simplified geometric model, we find that plastic motion or
thermoelectrically driven twists might naturally reproduce the observed
luminosities, timescales, and timing signatures. We further derive 'active
zones' in which rotationally-powered pair creation occurs via resonantly
scattered photons, beyond standard curvature deathlines for pulsars. All
cascades are generically accompanied by simultaneous (non-)thermal X-ray/UV
counterparts which might be detectable with current instrumentation.
