Despite its complex symbols, Lyra gradually begins to use the device fluently, believing that the Master wants her to pass it along to Asriel as a token of apology for the earlier attempted poisoning, orchestrated covertly by the Church.
Despite its complex symbols, Lyra gradually begins to use the device fluently--something which no adult can do as well as she. Lyra believes that the Master gave her the alethiometer to pass on to Asriel as a token of apology for the earlier attempted poisoning, which the Master only instigated under great pressure from the Church.