Upon finishing Death Plateau, players can compete the Supply and Demand achievement, in which they perform supply runs for Commander Denulth (requires a minimum Combat level of 18 to fully complete). Beneath Cursed Tides, a fairly lengthy quest that gives you a 10,000 experience combat lamp, (requires level 30 magic).
It is recommended that you finish these quests before training Magic, as it results in some quick Magic experience at low levels if the necessary items are bought.