Returns whether the player has learned a particular spell.
isKnown = IsPlayerSpell(spellID)
- boolean - true if the player can cast this spell (or a different spell that overrides this spell), false otherwise.
- Spells can be permanently or temporarily overridden by other spells as a result of procs, talents, or other spell mechanics, e.g.
- Querying the base (replaced) spell will also return true if any of its overrides are currently active.
- Querying an overriding spell may or may not return true even if that spell is currently known, depending on the particular spell.