The four-sided ones make me uneasy.

Caltroppers are experts in the use of caltrops: little spiky bits of whatever that are scattered on the ground in order to harm the feet of whoever moves through them. As a weapon, their effectiveness is as much about denial as actually dealing damage; this makes them a poor choice for a straightforward brawler but an excellent tool for a more tactically-minded battle administrator.

This is a weapon and subject to universal weapon rules.

Caltropper Make an area painful to walk in.
caret-right Barbed Pain the conditioned.
caret-right Hoppers Use in more situations.
caret-right Maker's Path Immunity to your own caltrops.
caret-right Scatter Wide Cover a larger area.
caret-right Toss Underfoot Make interruption attacks.

Caltropper

Offense plus-circleWelcome to Sharp Painful Object Land: As an action, you may scatter caltrops in a space of your choice in throwing range (0-10 meters) plus all adjacent spaces. Scattering caltrops counts as an attack action for purposes of double-attacks and all game mechanics that affect attacks (such as the Nauseous condition).

plus-circleAttack: Every time a creature travels 1 meter into one (or more) spaces that you've caltropped (including allies or even yourself) you automatically attack them with the effect. This does not require you to spend any actions or even for it to be your turn. Creatures that travel through multiple meters worth of caltropped spaces are attacked multiple times by the effect, causing damage to stack up extremely quickly. Creatures of size 6 or higher that occupy multiple spaces at once are still attacked by this effect just once per meter traveled regardless of how many caltropped spaces they are actually occupying.

plus-circleConditions: When the trigger die is 10+, this weapon inflicts its wielder's choice of the Crippled, Dizzy, or Sore conditions to its target.

plus-circlePain From Below: This weapon does not suffer failure chances from concealment, cover, or shields (from the Shieldbearer archetype).

minus-circleClearable: Any creature can clear the caltrops out of an adjacent space by spending an action to sweep them aside and move into the newly-swept space. Larger creatures that occupy multiple spaces can clear all adjacent spaces they will be moving into simultaneously as a single action. If a creature dies while in a caltropped space, the caltrops are all automatically removed from that space.

minus-circleAmmunition: Roll a trigger die when setting up the effect. When the result is a 1, mark off 1 Supplies. This weapon cannot be used if you have no Supplies remaining. Note that attacking with the caltrops does not consume or require any resources, only the initial setup does.
Condition Explanation
snail Crippled minus-circle The maximum distances of all movement and abilities that grant movement are reduced by one step on the standard distance scale (10 → 5 → 2 → 1 → 0).
ringing-bell Dizzy minus-circle Every time a movement action is taken, lose 1 Energy.

minus-circle Cannot dash (travel further in exchange for Energy) during a movement action.

plus-circle Movement made for free (without spending any actions) is unaffected.
player-pain Sore minus-circle Do not automatically regain lost Attention at the beginning of each round.

Barbed

Protection plus-circleCripple Hard: The caltrops are barbed, sticking painfully in the flesh of anyone unlucky enough to step on one. When a creature that you used this weapon to successfully inflict a condition on (Crippled, Dizzy, or Sore) moves at least two meters for any reason under their own power and by their own will (including free actions or any other effects), you may attack them with it again as a free action that is resolved immediately after the movement that triggered it. One such free attack is triggered by every two meters a target moves.

minus-circleSelf-Moves Only: If a conditioned target moves via riding on another creature or a vehicle, a Barbed attack is not triggered on them. If a conditioned creature is moved directly by another creature via a pushing effect or other similar ability, a Barbed attack is not triggered on them.

minus-circleCondition-Dependent: When a subject that you've applied a Caltropper condition to recovers from the condition, they are also no longer prone to attacks from this effect (they successfully pulled out the caltrop).

Hoppers

Offense plus-circleSpringy Bastards: Your caltrops are networked, or perhaps semi-alive. They occasionally bounce into the air, preventing any creature from avoiding them by jumping/floating/flying over them or using the Aerialist ability from the Acrobat archetype. Passing more than a meter above the surface where the caltrops are is still enough to avoid them, but any less is not.
Offense plus-circleCloudtrops: The caltrops can adjust their own buoyancy until they achieve equilibirum. When used underwater, they function normally as a loose cloud. When used on the surface of water, they float on the surface and affect anything else that floats through or breaks the surface in their area.
Offense plus-circleFree Fallers: The caltrops also function as a free-floating cloud when in an area that doesn't have any gravity.
Offense plus-circleSeekers: When attacking targets larger or smaller than yourself, size-based failure chances are reduced by 12.

Maker's Path

Protection plus-circleKnow The Way: You are immune to your own caltrops and can freely enter any space you've caltropped without being harmed. This ability does not protect your allies, only yourself.

plus-circleLead The Way: Your caltrops have a special failure chance of 6 against your allies, if any should happen to wander into the area of effect.

Scatter Wide

Offense plus-circleSpring-Loaded: When you set up caltrops, they are placed on the target space and every other space within 2 meters instead of only adjacent spaces.

Toss Underfoot

Offense plus-circleReactive Denial: Any time a creature enters a space within 5 meters of your location, you can quickly toss a caltrop under their feet as they move. This allows you to immediately attack them directly with the effect as an interruption to their movement, even though it isn't your turn.

minus-circleIntegrated Resource Check: Spreading and attacking with caltrops is all one action when using Toss Underfoot. When the attack's trigger die is a 1, then using the ability costs 1 Supplies.

minus-circleConservation of Action: Every time you choose to toss a caltrop underfoot, you get one less action on your next turn. You cannot toss caltrops underfoot more than twice per round.

minus-circleNo Scatter: Tossing caltrops underfoot does not leave any lying on the ground after. No spaces are made caltropped as a result of using this ability, it's a one-and-done kind of deal.