This article describes expertise development in a player group in the massively multiplayer online game World of Warcraft using visualization of chat log data. Charts were created to get a general sense of chat trends in a specific player group engaged in "high-end raiding", a 40-person collaborative activity. These charts helped identify patterns in the frequency of chat over time during two specific gaming sessions. The sessions represented significant moments in the raid group's history: the first time a particular monster, Ragnaros, was fought and one of the first times he was defeated. Differences between the two cases show differences in the raiding practice and are evidence of learned expertise. Based on this analysis, it is clear that this visualization process is a useful analysis tool within ethnographic accounts of expertise development.