Birthsigns and Zodiac for Old School Games

Zodiac Signs: each human character gets a Constellation assigned randomly at character creation. The Sign gives a +1 to a single saving throw type. (Other races do not get any sign, as they either do not care about the stars or have their own beliefs.)

The ten Star Signs:
1. The Key: +1 vs Poison/Death
2. The Worm: +1 vs Breath Attacks
3. The Tree: +1 vs Petrify/Paralyze
4. The Skull: +1 vs Spells
5. The Chalice: +1 vs Wands
6. The Lock: +1 vs Poison/Death
7. The Bird: +1 vs Breath Attacks
8. The Hatchet: +1 vs Petrify/Paralyze
9. The Heart: +1 vs Spells

10. The Torch: +1 vs Wands

Dungeons, tombs, ruins, runestones and so on may be aligned to a given Sign (usually the one of the original creator/builder/owner of the the place).

While in or near such a location, bearers of the matching sign get an additional +1 to the corresponding saving throw, bearers of the opposite sign get a -1 penalty to that saving throw, while other Signs are unaffected.

Stone circles are dedicated to the stars as a whole, and therefor give all sign bearers an additional +1 to their sign's saving throw. Those with no sign are unaffected by any of the above.

Plot ideas and hooks:
-The gate to the court of the Raven King can only be opened by those born under the same sign as him.
-A scholar needs one of each birthsign to perform a powerful scrying ritual. He has hired some slightly worried local civilians, but still needs a few more.
-A star cult has been kidnapping people of all walks of life who all were born around the same month.
-The local nobility has started organizing all celebrations, court activities and even civic duties around the horoscope.