Short answer:
If you don't need custom skill/spell messages then use TYPE_UNDEFINED when you call damage() or hit() functions for your skill/spell. TYPE_UNDEFINED is defined as (-1) and circle will not look for a message if that's the damage type.
Long answer:
Skill messages are used based on SKILL_* types and SPELL_* types defined in your mud.
The messages are used after damage() has been rolled for them, so when you call, for example:
Code:
damage(ch, vict, 0, SKILL_BACKSTAB);
The skill message for SKILL_BACKSTAB (which is skill 131 defined in spells.h) will be used:
Code:
#define SKILL_BACKSTAB 131 /* Reserved Skill[] DO NOT CHANGE */
Since the damage() function was called with 0 it will be considered a miss and a backstab-ery miss message will be displayed.
On the other hand if it were a hit you would call:
Code:
hit(ch, vict, SKILL_BACKSTAB);
The hit() function (defined in fight.c, just like damage()) would then be called to roll the damage for the skill, and if the roll ended up to be positive (let's say 10?) then damage would be called to deal that damage:
Code:
damage(ch, vict, 10, SKILL_BACKSTAB);
This time since damage has a >0 value, a backstab-ery hit message will be displayed.
It is the same for all skills/spells.
If you want to use generic messages for a skill/spell use TYPE_UNDEFINED when you call any of these functions:
Code:
damage(ch, vict, 10, TYPE_UNDEFINED);[
hit(ch, vict, TYPE_UNDEFINED);
This tells circle to not look for a customized message for that hit/damage roll and just display a generic message.
Unrequested friendly advice: you SHOULD use customized messages, they are much better and help to set the mood and keep all the RP in your mud. Just my opinion though hehe.