Wesnoth uses a custom markup language called WML, which can be edited by hand (it's similar to xml)

scenario configuration can be written using WML.

Sometimes, later scenarios assume the presence of certain NPC which join the player in previous scenarios. This can lead to problems when we jump to this scenario using :cl debug command - because we can jump over a scenario where that NPC joins.

we have WML syntax which has 'recall-or-create' semantics - to create required NPC if it is missing

More details here: http://wiki.wesnoth.org/GCI/RecallOrCreateConversion

To complete this task, convert 'The South Guard' campaign to use this mechanism

http://svn.gna.org/viewcvs/wesnoth/trunk/data/campaigns/The_South_Guard/scenarios/