diff --git a/src/help.rs b/src/help.rs
index 2c0b0c5..7eeebf5 100644
--- a/src/help.rs
+++ b/src/help.rs
@@ -5,6 +5,7 @@ pub fn parse_help_topic(input: &str) -> Option<HelpTopic> {
         "cofd" => Some(HelpTopic::ChroniclesOfDarkness),
         "dicepool" => Some(HelpTopic::DicePool),
         "dice" => Some(HelpTopic::RollingDice),
+        "cthulhu" => Some(HelpTopic::Cthulhu),
         "" => Some(HelpTopic::General),
         _ => None,
     }
@@ -13,6 +14,7 @@ pub fn parse_help_topic(input: &str) -> Option<HelpTopic> {
 pub enum HelpTopic {
     ChroniclesOfDarkness,
     DicePool,
+    Cthulhu,
     RollingDice,
     General,
 }
@@ -51,9 +53,11 @@ Rolling dice pools
 
 Command: !pool, !rp
 
-Syntax: !pool <modifiers>:<num>
+Syntax: !pool <modifiers>:<expression>
 
-Short syntax: !pool <num>
+Short syntax: !pool <expression>
+
+Expression Syntax: <num|variable> [+/- <expression> ...]
 
 Modifiers:
  n = nine-again
@@ -66,6 +70,35 @@ Examples:
  !pool 8 (roll a regular pool of 8 dice)
  !pool n:5 (roll dice pool of 5, nine-again)
  !pool rs3:6 (roll dice pool of 6, rote quality, 3 successes for exceptional)
+ !pool 10 + 3 (roll dice pool of 10 + 3, which is 13)
+ !pool myskill - 4 (roll pool of the value of myskill - 4).
+ !pool n:myskill - 5 (roll pool of myskill - 5, with nine-again)
+"};
+
+const CTHULHU_HELP: &'static str = indoc! {"
+Rolling Call of Cthlhu dice
+
+Commands: !cthroll (regular rolls), !cthadv (advancement rolls)
+
+Regular roll syntax: !cthroll <modifiers>:<num|variable>
+
+Advancement roll syntax: !cthadv <num|variable>
+
+Modifiers:
+ b = one bonus die
+ bb = two bonus dice
+ p = one penalty die
+ pp = two penalty dice
+
+Examples:
+  !cthroll 60 (make a roll against a skill of 60)
+  !cthroll spothidden (make a roll against variable spothidden)
+  !cthroll bb:30 (make a roll against skill of 30 with two bonus dice)
+  !cthadv 50 (make an advancement roll against a skill of 50)
+  !cthadv spothidden (make an advancement roll against the number in spothidden)
+
+Note: If !cthadv is given a variable, and the roll is successful, it will
+update the variable with the new skill.
 "};
 
 const GENERAL_HELP: &'static str = indoc! {"
@@ -74,6 +107,7 @@ General Help
 Try these help commands:
   !help cofd
   !help dice
+  !help cthulhu
 "};
 
 impl HelpTopic {
@@ -81,6 +115,7 @@ impl HelpTopic {
         match self {
             HelpTopic::ChroniclesOfDarkness => COFD_HELP,
             HelpTopic::DicePool => DICEPOOL_HELP,
+            HelpTopic::Cthulhu => CTHULHU_HELP,
             HelpTopic::RollingDice => DICE_HELP,
             HelpTopic::General => GENERAL_HELP,
         }