can you clarify that this game's messages are normal channel messages sent by other nicks in a channel? If so, you can use the ON TEXT event to intercept messages containing a string, either literal or wildcard or regex, then halt the original message, then replace it with an echo of your design. You could do something like
on ^*:TEXT:pattern goes here:#channelname:{
var %old_pattern text here
var %new_pattern text here
if (%old_pattern isin $1-) {
echo $chan $+(<,$nick,>) $replace($1-,%old_pattern,%new_pattern) | haltdef
}
}
It's much simpler to use variables like this when the text contains commas, otherwise you need to use $chr(44)'s instead of literal commas.
If your situation is different, then you need to better explain what your RPG game entails.