OSR: Minor Angels

You're more likely to find an angel in a bestiary or illuminated book than you are roaming Creation. They are rare and mythical. Their presence implies direct divine attention.

Creation of Adam, Quercia

Halo

HD 0 (1 HP) Attack 0 Defense 10 Cannot attack
Fly 20, hover Int 6 Mor 12
Wants to light the way or hover over the head of holy people.
Behaves like a roomba with different priorities
Appears alone, mostly.

A triangle of light the size of a dinner plate. Illuminates a 30' radius with soft white light. The light cuts through magical darkness. Halos are sent with a simple goal stamped into their forms. In a time of shadow, the devout might pray for a halo to appear and guide them home. A saint might have one permanently assigned to them. The Church says a halo's light banishes demons, cures diseases, purifies water, and burns the impure. It doesn't. It's just light. But anything that's afraid of light (some demons, disease spirits, the undead) might Save or flee anyway. A halo is a like the bow light on a battleship to them.

Chaos Angels 

HP 1d100, HD  HP/8 Attack 12 Defense 12 Attacks 1d6 melee per round, dealing 1d6 damage fire damage, exploding on a 6
Fly 12 Int 10 Mor 12
Save to reflect spells. Can shrink to fit any container. Can shout all languages.
Wants to ruin a plan
Behaves unpredictably
Appears in swarms of 1d4, exploding on a 4 if the plan is sufficiently complex
 
A black sphere made of thumbs and knuckles, with silver swords protruding and retracting from all sides. Makes a terrific noise, like an orchestra of apes sliding into a volcano. Cannot possibly hide. You can see it through walls and you can smell it (like a landfill) for miles.

The Authority can't see the future but He can make predictions. If you work on a plan contrary to His will there's a decent chance He can do nothing about it because of ancient laws and rules He created and cannot unmake. Free will is the most pernicious of them all. Paladins willingly exchange a portion of their free will to act on the Authority's behalf but Paladins are rare. Sometimes there is just enough room to squeeze a Chaos Angel into Creation. They are sent to stop plans. Say you wanted to rob a bank. You are an expert bank robber and you've planned for every outcome. A Chaos Angel explodes from your hat and stabs you to death. It might burn down the bank. It might shower you with gold. It might start a chain of events to devalue the local currency so that the bank is empty by the time you arrive. Unlike a Paradox Angel, a Chaos Angel has many ways to reach its goal.

Using these guys to thwart your players is the cheap and obvious method but it's also not very fun. A good plan should be rewarded, not penalized. Using them to thwart someone else's plan, or just have them show up, perform some inscrutable act, and then vanish in a cloud of incense, and then later on have the decisions the PCs made based on that act influence the outcome of an NPCs plan.

The Warning

HD 0 (1 HP) Attack 0 Defense 10 Cannot attack
Fly 20, hover Int 6 Mor 12
Wants to warn
Behaves like a balloon in a light rain
Appears alone and only for a few minutes

If you have been particularly devout, the Authority or one of His servants may send you a Warning of your impending death. The Warning is a grey hourglass with wings. It hovers in front of you. You feel a sense of peace, and know you will die within 72 hours.Unscrupulous people have faked Warnings using hourglasses, doves wings, and string. It's a staple in  bawdy rural plays.

Some particularly devout people, when confronted with their mortality, suddenly discover that they really don't want to die and that the prospect of Heaven and judgment is less appealing than a few more years in Creation. This is usually where the PCs get involved.

Anyone visited by the Warning fails all Saves for the next 72 hours. All hits against them count as critical hits. If they survive 72hrs, they will not die of old age, disease spirits, spells, or elemental damage for 1d100 years, plus 1 year for each Save they failed and survived. Weapons, falls, and strange effects can kill them. Their spirit will be forced to wander Creation for the rest of time, helpless and feeble, unless it can find a way to reincarnate and die.