A good start. How about this for symbiosis? BTW, is the spores attack just for reproduction?
It was originally, but we could make it a 1/week attack that causes some minor penalty as the spores try to infect their new host.
Symbiosis (Ex/Su?): Skullcap ivy prefers to grow on the head of intelligent mammals, replacing the hair of its host. The host reaps several benefits and a few disadvantages. For one, as long as the skullcap ivy has adequate sunlight and water, the host requires half as much food and water as usual (if kept out of sunlight, as in a dungeon, the ivy nourishes itself from the host's bloodstream but requires only half the food of a Diminutive animal, which is a negligible amount compared to a Medium or Small humanoid's daily intake). Furthermore, the host and ivy provide each other air to breath, so both can survive in airless or toxic? environments. On the other hand, while a skullcap ivy is immune to spells that target plant monsters, the host becomes vulnerable to entangle and similar spells. Specifically, if the ivy or the host is in the area of an entangle spell, the host must succeed at a Fortitude save, or the ivy will grow and start to strangle the host, causing suffocation if not killed. Also, during the spring months, the blooms of a skullcap ivy attract bee-like creatures. Any bee-like creature (such as a giant bee or a spider killer) will attack hosts of skullcap ivies before any other opponents.
Hmm, firstly it should be (Ex).
Secondly, it doesn't let the host live in vacuum or poison gas, it just stops them asphyxiating.
Finally, I don't much like the bee-creatures always attacking the host.
How's this strike you...
Symbiosis (Ex): Skullcap ivy grows on the head of intelligent mammals, replacing the hair of its host. The host reaps several benefits and a few disadvantages. For one, as long as the skullcap ivy has adequate sunlight and water, the host requires half as much food and water as usual (if kept out of sunlight, as in a dungeon, the ivy nourishes itself from the host's bloodstream but requires only half the food of a Diminutive animal, which is a negligible amount compared to a Medium or Small humanoid's daily intake). Furthermore, the host and ivy provide gasses for each other to breath, so the host will not asphyxiate if the air is low on oxygen (although they have no special protection from airless vacuums or poison gas).
On the other hand, while a skullcap ivy is immune to spells that target plant monsters, the host becomes vulnerable to
entangle and similar spells. Specifically, if the ivy or the host is in the area of an
entangle spell, the host must succeed at a Fortitude save, or the ivy will grow and start to strangle the host, suffocating them for [
1d4?] points of nonlethal damage per rounds until the host or the skullcap ivy is killed or the
entangle spell's duration ends. Also, skullcap ivy produces sweet-smelling blooms during the spring months which attract pollinating insects, including monsters such as giant bees. These creatures may attack the skullcap ivy's host if they try to prevent them feeding on the plant's nectar.