Owl Eyed (ta) and To Know the Gloom of Night (ta) wouldn't stack (both static? talent bonuses). The kink is what is a multiplier? Static bonus or a special bonus?
Heighten Senses (spell) looks like it will stack with either of the above, but the rulebook doesn't cover stacking of multipliers.
Other game systems (D&D) use additive multiplication based on the increase from the original number (x2 + x5 = x6).
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Owl Eyed [Skill] (ta)
Benefit: You can see double normal distance under a night sky. This does not give you the ability to see in complete darkness.
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To Know the Gloom of Night [Devout, Racial] (ta)
Benefit: You may see perfectly in non-magical darkness out to a range of 30’. You also see double normal distances under a night sky.
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Heighten Senses (spell)
Adaptation: Increase the CTN by 2 to instead gain the vision of an eagle, allowing you to see five times as far as normal.