Spy

A spy on the party's side is a bread-and-butter NPC ally: a courtier on retainer, a ranger's old contact in the Thieves' Guild, a hireling the party paid 50 gp a week to scout the next town. Spies are Neutral, not Lawful or loyal, and the alliance lasts as long as the pay is good or the cause is convenient. Treat them like a contractor, not a member.

The combat value is reconnaissance, not damage. Send the spy ahead with Stealth +6, Investigation +5, Perception +6 (and passive 16), and they come back with a count of guards, the layout of the keep's east wing, and one named NPC's daily routine. In a fight, the spy fires from the back at +4 with the Hand Crossbow for 12 damage on a hit (poison-laced bolts), and uses Cunning Action to stay out of melee range. They are squishy: 27 HP, AC 12, no martial training to speak of. If a frontline enemy reaches them, they Disengage and climb a wall, because that's what Climb 30 is for.

The price is the encounter. Spies want gold up front, and they renegotiate when the job changes. If the party suddenly wants the spy to commit a murder rather than collect a letter, the spy says no, the party says yes, and now you have a roleplay scene about the line between hire and accomplice. If the party tries to skip a payment, the spy reports their movements to the next bidder, and the campaign just got a new antagonist.

Give the spy a fake name they use with the party and a real name they keep written in a coded notebook. When the players find the notebook, the relationship changes.

A spy is a CR 1 humanoid whose stat block is built for the scene before the fight. Passive Perception 16, Stealth +6, Investigation +5, Deception +5, Insight +4: the spy notices the party first, knows they're armed, and has been listening to their conversation in the next booth. By the time combat starts, the spy already knows which PC has the magic item and is positioning toward the door.

Open at range with the Hand Crossbow: +4 to hit, 30/120 ft., 1d6+2 piercing plus 2d6 poison. That's an average of 12 damage on a hit, which is brutal at a CR appropriate for level 1 or 2 parties. Fire from cover or from a window across the alley, then use Cunning Action to Hide as a bonus action and reset for next round. Climb 30 lets the spy go up a wall mid-combat to break line of sight, which is the key trick: a spy on the rooftop is a spy the party's melee can't reach without burning two turns on Athletics checks.

In melee, switch to Shortsword: +4, 1d6+2 piercing plus 2d6 poison, same 12 average. Spies don't dual wield and don't multiattack, so they live and die on positioning and the poison rider. Cunning Action gives Dash, Disengage, or Hide every turn as a bonus action, which means the spy never eats an opportunity attack and never sticks around to be focused down. AC 12 and 27 HP say loudly that one good hit will take them out of the fight; play accordingly.

The spy does not fight to the death. Their job is information, not combat. Once Bloodied, Cunning Action Disengage and Dash for the door, and don't look back. If captured, they lie. Insight +4 means the spy reads the interrogator's tells, and Deception +5 means they pass most checks the party isn't actively prepared for. Whoever they were working for is the real campaign question.

Have the spy carry one document the party recognizes: a sketch of the wizard's tower, a name from a previous session, a coded note in a language one PC speaks. The fight ends in a clue, not a corpse.