"Helpless Targets: Regardless of attack throw and AC, all attacks on sleeping, paralyzed, or otherwise helpless targets automatically hit. If the attacker is not engaged by any other opponents, the helpless target can be automatically slain. Otherwise, a standard damage roll is made."
Sleeping creatures are helpless and can be killed in one round by unengaged opponents.
"Once a creature has been grabbed, the monster can automatically inflict damage each round with no attack throw necessary until the creature escapes. Grabbed creatures are helpless until they escape. To escape, the grabbed creature must make a successful saving throw versus Paralysis."
These rules are difficult to construe. If rule #1 is true, then the subordinate clause of rule #2 is redundant - ALL helpless creatures can be killed in one round by unengaged opponents. Likewise, if rule #1 is true, then rule #3 has a subordinate clause that is both redundant and deceptive. Once a creature has been grabbed, it is redundant to point out that "Once a creature has been grabbed, the monster can automatically inflict damage each round with no attack throw necessary until the creature escapes", and confusing not to point out that the monster ought to be able to automatically slay the grabbed creature if it is not engaged.
In ACKS Player's Companion, I use the phrase "helpless" a few times:
In Death Spells, under Effects, "target held helpless" costs 15 points.
In Death Spells, the description for Choking Grip is "1d6 damage per level capped at 1d (33x0.1=3.3) and target held helpless (15) (18.3 total), target 1 creature (x1), range 30’ (x0.6), duration concentration or until target makes save (x1.75), saving throw avoids effect (x0.5), arcane (x1), total cost 10"
Under Stinking Cloud, "Any creature caught within the cloud must make a successful saving throw versus Poison or be helpless due to nausea."
In Blast Spells, under Effects, "nausea-inducing" costs 10 points.
These rules are downright confusing. The description for Choking Grip does not state that the creature is held helpless, but does state that a "a choking creature cannot take any action (although it can still defend itself)." So "helplessness" in the spell description does not align with "helpness" as defined in ACKS, since the creature can defend itself!
Meanwhile, if Stinking Cloud's nausea does induce helplessness then it is more powerful than the not-helpless helplessness of the Death effect that costs more (15 to 10.)
"Sleeping creatures are helpless and therefore can be killed in one round by unengaged opponents."
"Once a creature has been grabbed, the monster can automatically inflict damage each round with no attack throw necessary until the creature escapes. Grabbed creatures cannot take any action on their initiative except attempt to escape. To escape, the grabbed creature must make a successful saving throw versus Paralysis."
In Death Spells, under Effects, add "target grabbed/unable to take any action" at a cost of 15 points.
In Death Spells, under Effects, change "target held helpless" to a cost of 40 points.
In Death Spells, the description for Choking Grip is "1d6 damage per level capped at 1d (33x0.1=3.3) and target grabbed/unable to take any action (15) (18.3 total), target 1 creature (x1), range 30’ (x0.6), duration concentration or until target makes save (x1.75), saving throw avoids effect (x0.5), arcane (x1), total cost 10"
Under Stinking Cloud, change text to "Any creature caught within the cloud must make a successful saving throw versus Poison or be nauseated. Nauseated creatures cannot take any action except to move up to their heavily-encumbered combat movement distance."
Hold Person causes helplessness. It is more expensive than Sleep because the paralysis can only be broken with a cure spell, whereas Sleep can be broke with, e.g. a slap to the face.
Hypnotic Pattern causes helplessness. It is more expensive than Sleep because it cannot be eas easily broken, but less expensive than Hold Person because it doesn't necessarily require a cure spell - it can be broken if the source of mesmerization is removed, for instance.
In any case, that was my sense in pricing those effects.
A creature makes a saving throw when the spell becomes effective on it and on each initiative roll thereafter.