A marker can protect the feature it's on from damage by:
Setting property "veto_fragmentation" to "veto" to protect it from fragmentation (Lee's Rapid Deconstruction spell).
Setting property "veto_shattering" to "veto" to protect it from shattering (Shattering spell).
Setting property "veto_disintegration" to "veto" to protect it from disintegration and nuking.
TODO: Document this. I'm not sure where to put info on this in docs/develop/level_design.txt
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