add eternal enhancement

magic.tex

@@ -497,6 +497,11 @@ This spell has the usual range, so if a caster cannot also cast at long-range, t
 
 \spelllevel
 
+\enhancement{1}{Eternal}{Make any magical item's effects permanent}
+
+This enhancement affects magical items such as Pocket Spells, Talismans, and Artefacts.
+The resulting spell lasts until it is cancelled by a command word, rather than dying after a number of scenes equal to its Potency.
+
 \enhancement{Varies}{Combined}{Add a second spell effect to the target}
 
 A secondary spell can be combined to throw at the same target.