Cat

A cat is a familiar, a witch's companion, a wizard's apprentice's apprentice, a tavern fixture, a barbarian's surprising emotional center. The stat block has no actions at all, which tells you everything: the cat is a character, not a combatant. AC 12, 2 HP, 40 ft. walk and 40 ft. climb, 60 ft. darkvision, Stealth +4, Perception +3 with passive 13. Run it for what it's good at, which is reaching places and noticing things.

In play, lean on the climb speed and stealth. A cat scouts a roofline, slips through a barred window, watches a meeting from a rafter, and reports back if it's a familiar with telepathic link. As a non-magical pet, it does the same things and the player narrates what it saw based on what it could plausibly understand (movement, threat, smells, the presence or absence of strangers). The 40 ft. base speed lets it cover ground faster than most party members in tight spaces.

The cat does not fight. It has no Rake, no Bite, no Claws on the stat block. If a player insists the cat attack, remind them: 2 HP, no proficiency, no listed action, anything that breathes near the cat kills the cat. The cat's job in a fight is to flee under the bed and remember who started it. A wizard with a cat familiar should be hiding the cat behind cover the moment swords come out, then dismissing it back to its pocket dimension if Find Familiar applies.

Give the cat a name and one specific quirk that nobody else at the table can predict. Sleeps in helmets. Hates the bard. Brings dead mice as offerings to the paladin. The cat is free worldbuilding. Let it work.

A hostile cat is a setup, not a fight. It's a witch's eyes on the party, a polymorphed enemy who hasn't dropped the disguise yet, a familiar reporting to a hidden master, an awakened beast loyal to whoever the party wronged last week. The cat itself has 2 HP and no attack. Killing it accomplishes nothing in the round it dies but a great deal afterward, because the thing the cat was reporting to now knows the party is the kind of group that kills cats.

Run it as a clue. The party notices the same black cat at three different inns. The cat sits on a windowsill outside the war room. The cat is in the throne room when the duke arrives, and the duke does not own a cat. Use the climb speed and Stealth +4 to keep it just out of casual reach: on a beam, on a rooftop, behind the privy. Passive 13 means it spots most clumsy approaches before they spot it.

If the players catch and confront the cat, decide what it actually is before they do. A familiar's controller takes psychic damage when it dies, which is a fact a wizard at the table will weaponize. A polymorphed scout reverts on death and now there's a corpse and a witness problem. A regular cat that was just a cat means the party has been paranoid for two sessions and that's its own kind of payoff.

Don't roll initiative against a cat. Resolve any chase as a single Dex (Acrobatics) check against the cat's passive 13 plus terrain, and let the result drive the next scene.