The first big discrepancy between Holmes and Cook in magic items is with magic swords. For Holmes:
Weapons with a plus after them are magical and the user adds the plus to his die roll for a hit.
That is not to damage (I find it intriguing that 3rd edition revives this concept with Master Work weapons, knowingly or unknowingly paying homage to this conception of magic weapons). In addition:
Any sword that is +2 or +3 against particular opponents (trolls, undead, etc.) does the indicated additional damage.
Thus a Sword +1, +2 vs. Spell Casters would be +1 to hit, and any time it did so against a Spell Caster, 2 would be added to damage. For Cook:
All magic swords are listed with a plus or minus. The number is the amount added to or subtracted from the result of the "to hit" roll and to the damage done.
Although Holmes curiously has most non-sword magic weapons behave like Cook's magic swords, this is a major discrepancy that must be dealt with. I could spend a lot of time arguing the merits of each approach and choose one over the other; however, I am not going to do that. This is an amalgam and an opportunity to solve problems not by going either/or but by choosing both/and.
There are clearly three types of magical weapons:
- Those that only affect the to hit roll.
- Those that affect the to hit roll and damage differently depending on the target.
- Those that affect both the to hit roll and damage.
Ring of Regeneration
In Holmes, rings of regeneration are described thusly:
regenerates injury to the wearer at a rate of 1 hit point per turn, even if the wearer is killed and dismembered, unless the ring wearer is treated as a troll.
Cook describes them this way:
The wearer will regenerate lost hit points at the rate of 1 per round. It will also replace lost limbs; a finger will re-grow in 24 hours and 1 limb can be replaced in one week. The ring will not function if the wearer's hit points drop to 0 or less. Fire and acid damage cannot be cured by this ring.
This is an intriguing mix. Whereas Cook's version is much better with a healing rate, Holmes' version is capable of rescuing somebody from death (though I would rule that they would have had to have the ring on when they died in order for it to function). Clearly, the Holmes version would be the rare ancient magic; however, the Cook version tantalizingly indicates that there are things where the intermediary civilization improved ancient magical techniques.
Potion of Giant Strength
Holmes describes a potion of Giant Strength this way:
Confers the full advantages of stone giant prowess, including doing 3-18 points of damage when scoring a hit, and having the same hit probability as a stone giant.
Cook gives this description:
The user will gain the strength of a frost giant. The effect may not be combined with other strength-adjusting magic items. The user may throw small boulders up to 200' to strike for 3-18 (3d6) points of damage, and will inflict twice normal damage on a successful hit when using any weapon.
The key difference between these two is that in Holmes, the imbiber attacks as a 9HD creature. The fact that Cook's version invokes the more powerful Frost Giant does not change the fact that it is less potent when used by low level characters. Again, this gives a tantalizing picture of an intermediary civilization trying to improve upon ancient magic and in some way coming up short.
Other Magic Items
There are several other discrepancies in magic items, but this mostly has to do with things like duration. For example, Protection Scrolls last 1d4 turns according to Cook and 6 turns according to Holmes. Keeping with the both/and theme there will be Greater and Lesser versions of these items (where current knowledge only allows Lesser items to be created).
This will also hold true for Wands of Detecting Secret Doors and Traps. Cook separates these into two different wands. Both exist, with the combo version being a lost technique.
In Holmes the Staff of Striking is only usable by Magic Users. In Cook they are also usable by Clerics. This is a bit of a conundrum, depending upon the metaphysics of the game setting. In my case, having (Christian) Clerics around is a relatively new thing. Thus, for my own purposes, Cook's version would be newer; however, I would adjust that depending upon what type of cleric you wanted using these staves and whether or not they are still around.
Medallions of ESP come in two varieties in Cook (30' and 90') and do not malfunction. Homles stats a 60' version and they have a 1 in 6 chance of malfunctioning every time they are used. The 90' version is ancient magic. Cook's 30' version is the intermediary magic. The 60' Holmes version is current magic.
Finally, in Holmes, the Potion of Flying only allows a move of 120' per turn. Cook has it at 120' per round. Thus, the Holmes version is more of a levitation kind of thing and I would probably just rename it and have it as a separate magic item, especially since Cook lists a Potion of Levitation but has no description for it.