It works mostly as described, though it requires substantial investment, is relatively risky, and is not necessarily as devastating as that thread suggests
This is a good build for combat, though it is relatively expensive in ways that may not be obvious from the specs. First I'll list why it's strong, and afterwards I'll go through some of the drawbacks:
The combination is a potent one. Tenebrous Form indeed makes it difficult to damage the Lasombra, Shroud of Night gives +2 difficulty to attack actions (usually) while also reducing Stamina dice pools by 2, each tentacle summoned by Arms of the Abyss needs to be dealt with separately by the target, and the tentacles can be used to restrain the target to at least some degree and also deal damage.
Controlling the tentacles requires little effort (in game mechanical terms, that's none), and the Lasombra doesn't even need to be all that close by to the area they're affecting. Plus, the min-maxed stats make each tentacle as powerful as possible for a typical-generation PC. The tentacles can come from any direction in an area covered by Shroud of Night, easily granting flanking and rear-attack bonuses (+1 and +2 attack dice, respectively). Presumably this is what the build description means by "multi-attacker penalties", as there is no such rule (in my recollection and quick review of the rules).
These advantages are substantial, and can give the Lasombra a real edge against many opponents, including some that wouldn't really be beatable any other way. Once the combo gets started, it can be very difficult to break (even beyond the downward spiral that VtM's combat system's brittleness imposes).
But it has some substantial drawbacks
- The build is seriously weakened if the Lasombra is not 9th generation
or better, with 8th generation being the preferred minimum
An 8th generation vampire can spend up to three blood points per turn, a 9th generation can spend up to two, and 10th or weaker can only spend one. These are important because using Tenebrous Form requires that three blood points be spent, and so can only be accomplished in one turn by an 8th generation or better vampire. Each use of Arms of the Abyss also requires a blood point be spent, and so spamming it requires a good generation rating (for the additional blood pool). This is expensive, requiring at least four dots in the Generation background to accomplish.
- The build requires several maxed out traits
When creating a highly specialized character that isn't such a big deal, but it costs a lot of freebie points and experience points to accomplish, meaning it has substantial opportunity costs (all the things you don't put points into, but that might have been useful) and necessitates successfully overcoming challenges in-game (and this build doesn't do much while it's developing; you have to have most of the pieces in place before it grants much of a reliable edge). Those 10-dice pools are important, and certain traits are required to be at 5 dots for the AotA tentacles to be reliably formidable.
- The build's most powerful effects suggest a reading of the rules that
is loose at best, and flat-out wrong at worst
In step 2, the section of the build description that says
Direct x Arms to hold the opponent, with x=half the number of Arms summoned, until the total number of grappling arms =the number of actions the opponent can achieve in a turn
The clear implication of the number of tentacles restraining the target is that the target is subject to the Hold combat maneuver, as being subject to that maneuver leaves the target immobilized and it takes one action per attempt to break a tentacle's grip. While immobilized by a Hold maneuver, a creature can take no actions other than trying to break the hold (V20 Core Rulebook, page 276).
This assumption is poorly supported. First, the Arms of the Abyss description does not reference the Hold maneuver, nor does it indicate that a target restrained by a tentacle is otherwise immobilized:
These tentacles may grasp, restrain, and
constrict foes. [...] Tentacles may constrict foes, inflicting (Strength +1)
lethal damage per turn. Breaking the grasp of a tentacle
requires the victim to win a resisted Strength roll
against the tentacle (difficulty 6 for each). (V20 Core Rulebook, page 189)
Restrain is not a game-defined condition or maneuver, and could indicate something like being tied by a tether just as easily as a boa constrictor-like full-body restraint. With enough appropriately positioned tentacles you could still get to an immobilized state, but that will be situation- and Storyteller-dependent. This is particularly important as it seems likely the build assumes that the target is immobilized, which would grant automatic hits to any attacker (including tentacles).
Why is the target not immobilized as per the Hold maneuver? Well, first off the maneuver itself is not referenced at all in the AotA description, immobilization is not mentioned in the AotA description at all, and the conditions for breaking a tentacle's grasp (a resisted Strength roll) is different from the condition for breaking a Hold (a resisted Strength + Brawl roll).
It's still a strong combo even so, but it's not as devastating as it would be if those assumptions of immobilization held.
- It relies on special, uninterrupted prep time to be effective
It will take a minimum of one turn to transform into Tenebrous Form, and a maximum of three turns. The transformation generally cannot happen on the same turn AotA is used (with an edge case of a 9th generation vampire, who can spend two blood points to begin the transformation on turn 1, and then spend the third blood point on turn 2, leaving one additional blood point to be spent on AotA on turn 2 as well).
These time limitations are compounded by the fact that the build does not have Celerity, and so definitely incurs penalties for attempting multiple actions per turn. Trying to use more than one Discipline per turn means splitting the smallest dice pool used in any of them, which really undercuts the "spam AotA tentacles" phase of the plan. Even Celerity wouldn't necessarily help with this, but there are some situations in which it might.
You don't really need multiple uses of AotA per turn with a maxed out dice pool (especially if using Discipline Prodigy to reduce the difficulty), as you're very likely to get a good number of tentacles per single use. But it's important if the Lasombra doesn't have "free" turns to transform, set up Shroud of Night, and get tentacles on the field immediately (which is important to the strategy).
- Benefits may not stack as intended
Shroud of Night imposes penalties, including Blind Fighting, on most targets. But it's not a guarantee that that penalty applies:
Blind Fighting/Fire: Staging attacks while blind
(or in pitch darkness) usually incurs a +2 difficulty (V20 Core Rulebook, page 274)
Emphasis on usually mine. A Storyteller may well rule that it's not so hard to hit a target that is wrapped around one's own body and can't move while doing so, negating the penalty. Not a huge deal overall, but there are plenty of builds that can do serious damage to tentacles in short order. This is especially true when the opponent the tentacles are grabbing is not immobilized, which the opponent will not necessarily be (as above).
- The strategy is predictable and brittle
It's a strong opening, especially with enough time to prepare. But if a target escapes the area affected by Shroud of Night and dodges or breaks free from any single use of AotA they have several options.
Depending on the conditions of the area where the fight is taking place, there may be large stretches where AotA can't reach the target, or only a limited number can reach the target at once.
Using the Dodge maneuver (which can also be used without penalty within Shroud of Night's area) can prevent tentacles from latching on, while Block and Parry may or may not be penalized in SoN's area but definitely aren't in better lighting. If parrying, the target can both fend off each tentacle and damage it simultaneously. Further, a character giving a turn to defending doesn't suffer the normal dice pool penalties for splitting actions (V20 Core Rulebook, page 275).
Only certain builds can reliably fight the tentacles that way, but it's not implausible that the right opponent can overmatch the tentacles and force the Lasombra to run out of blood. In any case, there are no surprises or variations to the strategy-- the Lasombra is specialized around this, invests a nontrivial amount of blood into executing it, and has few options once it's initiated the process (Tenebrous Form makes the vampire very difficult to damage, but also prevents it from doing a lot of things it normally could).
Catastrophic failure states for this setup do exist, and the more often this strategy is used the more likely it is that you'll encounter one.
- Tenebrous Form introduces special counter-tactics to this approach which are unlikely to be mitigated
The key weakness of TF is its penalty to resisting Rötschreck. Many vampires will not casually have the materials and presence of mind to make use of that, but if the Lasombra is exposed to fire and/or sunlight they can be driven off, immediately losing the ability to manipulate the tentacles in the process. It might be a desperate move for a vampire, who is only marginally less susceptible to Rötschreck, but being the target of the combo once it's started is already a pretty desperate situation.
Another key drawback of TF is that the Lasombra probably cannot gain additional blood points while transformed, placing a sharp limit on how long it can carry out the plan. I know of a single, offhanded reference in game lore to regaining blood while in TF being possible, but it has no mechanical description and the transformed Lasombra can't physically attack or manipulate physical objects by itself.
- It becomes less effective with more opponents
That's always true, really, but this strategy uses a lot of tentacles at once to harass each enemy combatant. A modest number of opponents, even weak ones, can overcome the advantages of the tentacle horde. Depending on how they're equipped, they can also eradicate the tentacles nearly as fast as they appear! And disposable mooks are not hard to come by, even for a weak vampire.
- It's not enough to shatter the game, and a Storyteller can easily
deal with it in many ways
There's more to the game than combat, especially combat with a small number of opponents. A character specialized around fighting with a single strategy which is expensive to enable is likely to struggle in many other situations. Enemy groups that have heard of or observed the strategy, or simply know something about Lasombra, can prepare specific countermeasures to blunt its effectiveness. And powerful enemies, which are appropriate antagonists to such a Lasombra, can easily have hard counters like high Stamina and Fortitude ratings, high-powered Thaumaturgy powers that can blast a Lasombra in TF, and other options.