Resultados posibles:
custodiabas
-you were guarding
Imperfecto para el sujeto del verbo custodiar.
custodiabas
-you were guarding
Imperfecto para el sujeto vos del verbo custodiar.

custodiar

El prisionero que custodiabas.
The man you were guarding. What happened to him?
Palabra del día
el muérdago