Thief Guilds: Assasins and Investigators

Beings Guilds (GLOG thief subclass) along the lines of Lexi's template. (I've also both directly lifted some of the skill trees - which, from the initial templates, seems in line with the philosophy - and the idea behind my favorite single power, which being the Historian's "Speak with Art" ability.)

Assassins' Guild

Starting Equipment: dirk, facemask, poisoner's kit, lockpicks,
Skills (2, d6): 1. Hitperson, 2. Internal Security, 3. Secret Executioner, 4. Serial Killer, 5. Spy,  6. Zealot

• Alexipharmikon
1. You can detect the presence of poison in any substance by sniffing or licking it. Interacting with it on this level does not harm you.
2. You are immune to all common poisons. Preparing for a week (building up your immune response, changing your diet, adopting a specific prayer regime) allows you to develop an immunity against one esoteric poison that you have isolated a sample of and researched before. 
3. You gain the ability to Speak With Poison.

• Casing
1. By spending a day observing someone's movements, you may Case them. You have advantage in any attempt to research, impersonate, or fight anyone you have Cased.
2. If you have Cased someone, you can impersonate them almost perfectly. Spend a scene in preparation; referee secretly rolls 1d6; on anything but a 6, you have successfully impersonated them as long as you maintain perfect confidence in your con.
3. If you have spent over a week impersonating someone, you gain perfect knowledge of what they would do. You count as them for the purposes of magical identification and "being" them in the eyes of the universe.
• One and Done
1. For the first attack you make in the first round of combat, reroll 1s; explodes if surprise round.
2. As above, but reroll 1s and 2s.
3. As above, but reroll 1s, 2s, and 3s.
• Opportunist (as Thief)
1. Whenever you would gain advantage to hit, you may also roll damage with advantage.
2. Whenever you would gain advantage on a roll, you may reroll 1s.
3. Whenever you would gain advantage on a roll, you may roll 3 results instead of 2 and take the best.
• Just an Accident
1. Deal +1 damage with all improvised weapons; double all falling damage directly caused by you.
2. Whenever you deal lethal damage to someone, you may spend a scene either tidying up (such that it looks like an accident) or leaving a calling card (such that you gain a Terror Point, which may be 1. expended to gain advantage on intimidation rolls 2. used by your GM for purposes up to them).
3. You no longer have to choose between making something look like an accident and getting Terror Points; everything is provably only an accident, but only contributes to the atmosphere of terror.
• Prepwork (as Thief)
1. On a 1 in 6, you may declare that you've set up a minor environmental effect nearby in an area that you would've had access to within the recent past, and trigger that effect.
2.  One automatic success per day, then 2 in 6 for each following attempt.
3.  3 in 6 for each following attempt, and you can have retroactively set up effects in any area you plausibly could have had access to at any time in the past.

Investigators' Guild

Starting Equipment: mark of office, change of clothes, magnifying glass, brass knuckles
Skills (2, d6): 1. Heresiologist, 2. Internal Investigations, 3. Journalist, 4. Private Eye, 5. Secret Police, 6. Town Watch

• Alexipharmikon (as Assassin)
1. You can detect the presence of poison in any substance by sniffing or licking it. Interacting with it on this level does not harm you.
2. You are immune to all common poisons. Preparing for a week (building up your immune response, changing your diet, adopting a specific prayer regime) allows you to develop an immunity against one esoteric poison that you have isolated a sample of and researched before. 
3. You gain the ability to Speak With Poison.
• Appraisal (slightly changed from Historian's)
1.  You can tell the rough value (within an order of magnitude) and historical/geographic provenance of items, architecture, etc. You know how to dismantle them to get 20% value from the more manageable components, rather than the ordinary 10% for defaced art.
2. You can identify that an object, effect, or creature is illegally obtained on sight. Gain the ability to Speak with Contraband.
3. Gain the ability to Speak with Crime.
• Casing
1. By spending a day observing someone's movements, you may Case them. You have advantage in any attempt to research, impersonate, or fight anyone you have Cased.
2. If you have Cased someone, you can impersonate them almost perfectly. Spend a scene in preparation; referee secretly rolls 1d6; on anything but a 6, you have successfully impersonated them as long as you maintain perfect confidence in your con.
3. If you have spent over a week impersonating someone, you gain perfect knowledge of what they would do. You count as them for the purposes of magical identification and "being" them in the eyes of the universe.
• Danger Sense (as Historian)
1. 3/6 chance of acting in surprise round when ambushed, advantage on saves against effects you haven't seen yet.
2. Always act in surprise rounds; always act first in initiative order.
3. Once, you may cheat death.
• Forensic Specialist
1. You gain the ability to Speak with Dead, but only with those who have died violently within the last week whom you found that way, about the circumstances of their death. 
2. If you can Case someone (as above), you can Case them by Speaking with at least three of their victims from three separate incidents.
3. Remove the time restriction from the first ability above. You can Case someone by Speaking with Dead them.
• Truncheon Master
1. You may deal nonlethal damage with any weapon.
2. Whenever you roll a hit against someone and deal nonlethal damage to them, you may immediately attempt an attack (with nonlethal damage) against another adjacent opponent whom you have not  attacked this turn.
3. You may take the A template for any fightery class, but only use the abilities gained thereby to deal nonlethal damage.