This is related to buffs and debuffs and how they interact. There are some spells that when applied, will cause other spells to fail, which I call a "Counterspell".
This occurs when a buff and debuff affect the same stat type, for example, Pine Needles (+30% Empower) and Infirm (-30% Empower).
A buff can be applied over top of an active debuff, but a debuff cannot be applied on top of an active buff.
This is not always intuitive as to what can act as a Counterspell. So far, these are the interactions I have tested:
- Infirm cannot apply on top of Pine Needles or Giant's Strength
- Heat Up cannot apply on top of Pine Needles or Giant's Strength
- Astral Body cannot apply on top of Magic Shield or Sense Danger
- Numbness CAN apply on top of Bless
- Medusa Gaze cannot apply over Replicate or Ultimate Evasion
Interactions that I have noted, but not tested yet:
- Fairy Fire and Bless (likely follows Numbness and Bless interaction)
- Astral Body and Dominate (likely follows Astral Body and Magic Shield interaction)
- Astral Body and Astral Force (likely follows Astral Body and Magic Shield interaction)
- Infirm and Fire Trap (likely follows Infirm and Pine Needles interaction)
- Infirm and Astral Force (likely follows Infirm and Pine Needles interaction)
- Entangle and Unlock
- Alter Reality and True Sight
- Exhaustion and Grance