I've experienced an issue concerning the Will-o'Wisp a few times, and I would appreciate it if people could weight in. There is a strong disagreement, and I'm hoping this thread can be useful to settle the matter.
Will-o'-Wisp states that it has Natural invisibility in it's Defensive Abilities.
Natural Invisibility (Ex) Will-o’-wisps have the ability to extinguish their natural glow as a move action, effectively becoming invisible, as per the spell.
Universal Monster rules
This ability is constant—the creature remains invisible at all times, even when attacking. As this ability is inherent, it is not subject to the invisibility purge spell.
Format: natural invisibility; Location: Defensive Abilities.
I know there are many creatures that have things listed in their stat block that you can refer to the rules in the Universal Monster Rules, but in their stat block they write out unique things. Do you ignore what specific things are listed in their stat block and go with the Universal rule, or do you follow their specific text in their stat block?
In this matter specifically does the Will-o'-wisp
1. stay invisible for the end of time by never shining light once it uses its ability?
2. The creature is never visible in the first place because it is always invisible, and it is the glow that turns on and off by using a move action and on the conditions of the invisibility spell (hostile actions turn it visible again etc.) the glow will return?
3. The creature is visible and glows, but as a move action can turn invisible as per the spell (hostile actions turn it visible again etc.) while extinguishing it's light?