Table defines if auras in one spell_group can't stack with each other.
Note: The table doesn't affect persistent area auras stacking or passive auras stacking (they can stack always) or spells belonging to same spell_rank (they are always subject of SPELL_GROUP_STACK_RULE_EXCLUSIVE rule)
Rule deciding which spell effect will prevail over the others as they are not stackable.
|0||SPELL_GROUP_STACK_RULE_DEFAULT||No stacking rule defined - placeholder|
|1||SPELL_GROUP_STACK_RULE_EXCLUSIVE||Auras from group can't stack with each other|
|2||SPELL_GROUP_STACK_RULE_EXCLUSIVE_FROM_SAME_CASTER||Auras from group can't stack with each other when cast by same caster|
|3||SPELL_GROUP_STACK_RULE_EXCLUSIVE_SAME_EFFECT||Same effects of spells will not stack, yet auras will remain on a target|
|4||SPELL_GROUP_STACK_RULE_EXCLUSIVE_HIGHEST||Only highest effect will remain on target|
A spell should be in only 1 group with this stack rule.