Four Against Darkness supplements add a wide variety of new mechanics to the game, and they are generally compatible with each other, so you can pick and choose which you'd like to use in your own game. Some supplements are greatly enhanced by owning others; the Druid and Wood Elf from Wayfarers and Adventurers, for example, will be much more interesting and useful if you're playing a woodlands dungeon, which are described in The Crucible of Classic Critters, and many supplements have extra rules relevant to expert parties from Four Against the Abyss.
These mechanics can be used in any game with any combination of supplements.
| Mechanic | Location | Notes |
|---|---|---|
| Animal Companions | CCC, pp. 11–12 | Pets that fight at your side. |
| Banks | TAG, pp. 9-11 | A place to store your gold. May be robbed! |
| Blossoms Spells | TCOTFD, pp. 26–27 | New spells usable by wizards and alchemists. |
| Capture | CCC, p. 7 | Monsters may attempt to capture rather than kill the party. |
| Character Milestones | W&A, pp. 33–41 | Simple quests, often offering permanent bonuses as rewards. usually not repeatable. |
| Character Traits | W&A, pp. 22–32 | Positive or negative effects to make characters more unique. |
| Expert Characters | 4AA, passim | Characters of levels 5–9. |
| Flying Monsters | CCC, p. 6 | |
| Food Rations | CCC, p. 5 | |
| Gambling House | TAG, pp. 16, 21 | Gamble for a chance at money or clues. |
| Highest Character Level (HCL) | TCOTFD, p. 21 | A system for adjusting monster strength to match the party's level. |
| Leaders | 4AA, pp. 7–9 | |
| Madness | 4AA, p. 34 | |
| Martial Arts Training | TAG, p. 15 | Allow fighting bare-handed at -1 instead of -2. |
| Moneylenders | TAG, pp. 16–17 | Borrow money from unsavory people. |
| Mounts | CCC, p. 13 | Creatures that can fight alongside you or carry items for you, outdoors only. |
| Poison Resistance Training | TAG, p. 15 | Allow rerolling a failed poison save. |
| Potion Making | TCOTFD, pp. 70–105 | Instructions are given for creating your own potions and harvesting ingredients from other monsters. |
| Professionals | 4AA, pp. 30–33 | Hirelings whose services you may purchase between adventures. |
| Settlements | TAG, pp. 4–5 | Rules for generating towns, and moving between them on a hex map. |
| Stealth | TAG, pp. 6–8 | |
| Subduing Monsters | CCC, pp. 7–8 | |
| Training | 4AA, p. 35 | Spend gold to get XP rolls. |
| Troupe Play | TAG, pp. 1–4 | Rules for playing more than four characters (in rotation). |
| Woodlands Dungeons | CCC, pp. 3–4 | |
| Wooing | TCOTFD, pp. 28–36 | Mostly used in TCOTFD, a satyr can attempt to woo any female humanoid or near-humanoid creature. |
These mechanics are of interest largely or exclusively for playing content in the supplement in which they occur.
| Mechanic | Location | Notes |
|---|---|---|
| Melancholy | TCOTFD, p. 21–22 | |
| Mesmerizing | TCOTFD, p. 23 | |
| Seduce | TCOTFD, p. 23 | |
| Treasure Maps | TAG, pp. 16, 32–33 | A chance at a dungeon or encounter with increased rewards. |
New items you might create or purchase between adventures.
| Item | Location | Notes |
|---|---|---|
| 10' Pole | TAG, p. 14 | Check for traps and improve searching. |
| Aspergillum | TAG, p. 19 | Light crushing weapon, filled with holy water. |
| Bag of Carrying | TAG, p. 13 | Increase your carrying capacity. And your being-stolen-from capacity. |
| The Balm of Nicodemus | CCC, p. 10 | Potion, removes monster immunity to non-magical weapons. |
| Blessing Tags | TAG, pp. 11–13 | Pre-pay for a blessing (at a discount). |
| Bolas | W&A, p. 55 | Light ranged crushing weapon used for capturing enemies. |
| Boomerang | W&A, p. 55 | Light ranged crushing weapon. |
| Flail-Axe | TAG, p. 18 | A one-handed slashing weapon. |
| Flask of Flammable Oil | TAG, pp. 17–18 | A throwable weapon. |
| Gems and Jewelry | TAG, p. 13 | Covert gold to gems, so you can carry more. |
| Good Boots | TAG, p. 17 | Defend your feet. |
| Horn | TAG, p. 18 | Rally the party. |
| Lantern Hook | TAG, p. 14 | Carry a lantern on your shield, to free up a hand. |
| Leafsteel Armor | W&A, p. 51 | Craftable Light Armor that works like Heavy Armor. |
| Resurrection Tags | TAG, p. 11 | Pre-pay for a resurrection (at a discount). |
| Very Nutritious Food | TAG, pp. 14–15 | Allow rerolling a failed die roll. |
| Wineskin | TAG, p. 18 | Modified save rolls. |
New spells you can find on scrolls to add to your wizard's repertoire.
| Spell | Location | Notes |
|---|---|---|
| Destroy Abberration | W&A, p. 48 | Damage spell vs. Weird Monsters. |
| Distant Communication | W&A, p. 48 | |
| Illusion | W&A, pp. 47–48 | |
| Illusionary Bridge | W&A, p. 48 | |
| Surge of Strength | W&A, pp. 48–49 | Use two-handed weapons with one hand and break down doors automatically. |
| Wall of Ice | W&A, p. 48 | Enable safe withdrawal from combat. |
The Crucible of Classic Critters has rules for making your own animal companions, but also includes some examples, and supplements provide more.
| Animal | Location | Notes |
|---|---|---|
| Bearwolf | W&A, pp. 52–53 | |
| Forest Shadow | W&A, p. 52 | |
| Hawk | CCC, p. 11 | |
| Owl | CCC, p. 11 | |
| Peacock | CCC, p. 11 | |
| Warhoud | CCC, p. 11 | |
| Wildcat | CCC, p. 12 |