//the CALL

Spell.CastSelfSpellByID(18540, ret => Me.CurrentTarget != null && Unit.IsTargetWorthy(Me.CurrentTarget), "Summon Terrorguard"))),

//The Method
        public static Composite CastSpellByID(int spellid, CLU.UnitSelection onUnit, CanRunDecoratorDelegate cond, string label)
        {
            var spell = WoWSpell.FromId(spellid);
            return new Decorator
                (context =>
                {
                    if (!cond(context))
                    {
                        return false;
                    }
                    if (spell == null)
                    {
                        CLU.TroubleshootLog("SpellID not found: {0}", spellid);
                        return false;
                    }

                    var target = onUnit(context);

                    if (target == null)
                    {
                        CLU.TroubleshootLog("Target not found.");
                        return false;
                    }

                    var canCast = CanCast(spell, target);

                    if (!canCast)
                    {
                        return false;
                    }

                    return true;
                },
                 new Sequence
                     (new Action(a => CLU.Log(" [Casting] {0} on {1}", label, CLU.SafeName(onUnit(a)))),
                      new Action(a => SpellManager.Cast(spell, onUnit(a)))));
        }