They seem to go around always veiled. Are you assuming that the veil is umi, rather than light manipulation?
I'm assuming that with All Things Betray we could see past it.
I also have an alternative, and I think more ambitious idea:
1) Use gossamer we got, and, together with Bob, Harry and Lydia make a knockout / paralytic that would work on a naagloshii for at least one minute. That's essentially an overpowered version of a one dot Alchemy recipe
• A powder that, when mixed with alcohol, induces slumber almost immediately. The target must roll Stamina (difficulty 8) or spend a point of Willpower to stay conscious; he must remake this attempt (at a -1 to Difficulty each time) every round until he succumbs or the drug no longer has a chance of success. Unconsciousness lasts for (10 - Stamina) hours, during which they cannot be roused. Vampires are almost immune to this drug (+2 to Stamina, add Fortitude, and effects, if they succumb, last 10 - (Stamina + Fortitude) minutes), but werewolves in their "normal" form (Homid or Lupus) are susceptible (+2 to the roll).
turbocharged to exalted levels by both being made by a celestial exalt (lots of dice), made by a collective of people (Harry, Bob, Lydia, borrow Order's Cauldron or invite the order to participate) and a use of gossamer, which can explicitly be used to make impossible substances, and can probably be modeled as a six dot alchemical recipe
•••••• A legendary substance that takes on the exact properties needed at a given time. There's a -2 difficulty to craft an object from it, and a similar difficulty to any actions taken using that object as a weapon, tool, or otherwise.
This requires buying Alchemy path to one dot.
2) Deliver the drug to Naagloshii. Either a dart, or coat our sword with it, buy Anonymity Through Propriety and sneak it in (does it eat normal food? I would assume so, if only for pleasure), or get a fae stealth specialist to do it.
3) Buy and use Emerald Circle Binding
Emerald Circle Binding
This powerful spell allows the sorcerer to bind a
spirit into her service. It doesn't protect her from the spir-
it's attempts to visit violence upon her during the course
of the binding, and so is best performed after defeating
or bargaining with a spirit, or in the company of allies
who can protect her while she casts the spell.
System: This spell must be performed in the im-
mediate presence of the target spirit (being on the ma-
terial side of the Gauntlet within an area correspond-
ing to the spirit's location in the Penumbra counts).
The Exalt claps her hands and spend 1 Essence, pre-
venting the spirit from leaving her presence while she
performs the rest of this spell. She must then spend 5
Essence and make an extended Intelligence + Occult
roll against a difficulty of the spirit's Gnosis rating.
Once she accumulates a total of 10 successes, the spirit
is bound to her service for a year and a day.
Alternately, if the Exalt has defeated a spirit in bat-
tle within the last two turns, clapping her hands and
spending 1 Essence stops the spirit from dissipating
and draws its Essence temporarily back together. In
this case it remains helpless to oppose her during the
remainder of the spell, as her sorcery is the only thing
preventing its discorporation.
A sorcerer may keep as many bound spirits at a
time as her Essence rating. Any spirit more powerful
than a gaffling or jaggling is beyond the scope of this
spell to bind.
Occult Excellency + Emerald Circle Binding is 6 essence. That's three combat turns, which, if I recall correctly, is roughly 18 seconds (6 seconds per turn, please correct me if I am wrong). In this time we don't need to kill a naagloshii. We need only to survive in its presence.
WoD Wendigos are Gnosis 7. Let's assume Gnosis 9 (because 10 is the maximum possible). So, we'll be rolling at difficulty 8 (9 - 1 BSM), 5, if we are using CCC or trigger TLF (9 - 1 BSM - 3 CCC/TLF), or 3 (9 - 1 BSM - 3 CCC - 3 TLF). We need 10 successes total. We might be able to lower the dificulty if we study what kind of oaths naagloshii betrayed and is still bound by that give Navajo power over it and/or if we discover Molly to have Navajo blood. We should be rolling 20 to 22 dice (18 from Intelligence + Occult, 2 from WHWH, 2 from stunt).
Worst case scenario (20 dice, DC 8), we'll need two turns to accumulate 10 successes. Depending on whether the counting starts at the moment we start spending essence or the moment we spent it, that's either 3 or 5 combat turns that we'll need to survive against Naagloshii, at which point it's bound by Ancient Sorcery and is compelled to obey us by an absolute effect.
Naagloshii is most likely a Jaggling in the spirit hierarchy:
Jagglings
Most of the dangerous spirits the Garou fight in the
Umbra are Jagglings. Nearly all of them can be considered
part of the Weaver, Wyrm, or Wyld — in fact, some are
fanatically devoted because they're formed from a portion
of their patron or master. Pattern Spiders, Nexus Crawlers,
Banes, and Englings are all common examples. Most loyally
serve an Incarna, though a few serve Celestines directly.
Some develop (or earn) free will and independence from
the patron, although this is more common on the remote
fringes and smaller realms of the spirit world. Werewolves are
intimately familiar with the Jagglings who teach them Gifts,
including a wide variety of animal spirits who demonstrate
the instincts and intellects of creatures in the physical world,
albeit in very idealized ways. A Jaggling may also serve as a
reservoir of spiritual power, as is shown by Englings capable of
providing Gnosis to an entire pack (or even a sept) of Garou.
In Werewolf the Apocalypse 20th Anniversary edition the hierarchy is given as (from top to bottom)
Celestines
Incarnae
Jagglings
Gafflings
Mab is an Incarnae. Naagloshii, for all it's a semi-divine being, is not Mab's equal, so counting it as a high level Jaggling with high Gnosis seems reasonable.
To make this work, we spend XP on Alchemy (we would have done so already), possibly on some stealth charm (again, probably something we'd need to do anyway), and Emerald Circle Binding (our first Ancience Sorcery! Squeee!). Resource-wise we also spend gossamer to make an ultra potent knockout posion (we would also want to spend a Crown on both the gossamer before the making to find more of it, and on the poison afterwards, to learn how to make such things without gossamer). We gain a naagloshhii servant for a year and a day. In that year, with appropriate charms (a lot of social excellencies, Heart-Carving Wind, Chilarity Prohibition Index, Spawning Pit Sanctification, etc) we can either reform or destroy naagloshii completely, after also milking it for all the lore and divine wisdom it has.
Alternatively, we spend XP on Alchemy. One dot recipe from Sorcerer's Companion is
• A potent poison (one with a Toxin Rating of 7)
I wasn't able to find what "toxin rating 7" translates to, narratively, sadly. I think we can safely say that it's a magical strong poison, so the following effect probably applies:
• Strong Poison: The character takes between one
and three levels of lethal damage per turn. Poisons have
a maximum amount of damage they can apply, usually
between five and ten levels of damage. A werewolf can
regenerate this damage normally, but until the poison
has run its course and all the damage has been healed,
subtract one from all dice pools. The only toxins to have
a significant effect on werewolves are supernaturally
enhanced, and as such deal lethal damage.
Depending on whether we can further enchant the poison via using gossamer, and a crown to ask "how do I make the poison I am making as deadly as possible (to naagloshii)?", I think we can push it up to the highest effect (i.e. ten levels of damage per turn)
We can assume that naagloshii would have either an equivalent of
• Resist Toxin (Level One) — The werewolf's body
is hardened against toxins of all sorts. A rat-spirit teaches
this Gift.
System: The werewolf is permanently immunized
to mundane poisons, from arsenic to alcohol, and adds
three dice to resist the effects of Wyrm-enhanced toxins.
This Gift may be turned off and on at will (such as for
enjoying alcohol).
or
• Survivor (Level Five) — The werewolf becomes
an ultimate survivor, with no need of food, water or sleep.
She ignores temperature extremes, natural diseases, and
poisons. Wyrm toxins have only half their normal effect
on her. A tortoise-spirit teaches this Gift.
System: The player spends one Gnosis point and rolls
Stamina + Survival. The effects last for one day per suc-
cess. By spending a second Gnosis point, the character can
gain three extra points of Stamina, and suffers no wound
penalties, but the Gift will prematurely expire 10 rounds
later. The Garou must sleep for at least eight hours when
the Gift wears off, and he awakens ravenously hungry.
So, this would be 5 levesl of lethal, possibly aggravated if we can apply Transcendent Anathema to it, and possibly with 4 more levels of aggravated damage from GSNF per turn. On top of us attacking. That might be a viable strategy.
We'll need to buy alchemy, and we'll need to get into a striking range of naagloshii to deliver the poison. Both might be doable.