Heir runes stack multiplicatively so when we equip all three runes, by simply adding values 30%+40%+50% we would get +120% but in-game BE increase from 742 to 2025 which is +1283 / +172.91% therefore stacking effect is +53.11%.

Do runes in bloodborne stack?

Notes. Players can stack all 3 "Moon" runes to acquire a whopping 60% more Blood Echoes. However, since one of them gives only 10%, it might be in the player's best interest to only equip the two best runes of this kind in order to leave a rune slot for a better rune.

Are caryll runes one time use?

You can only possess one rune of the same type and strength unless it is dropped by NPCs on death like William and can be glitched to received more than one Eye 2 runes. A Madman's Knowledge will replace it if you acquire it again.