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If you have a multitude of Tier (2) abilities, you are likely no longer [i]just[/i] a "lowly" Tier (2). Some abilities synergize well or even intentionally while others are strength in numbers or philosophy of jack-of-all trades. Compounding and totality are factored into a character as a whole, with the tier examples be general guidelines; the majority of powerful spells you noting at Tier (4) being those most often seen in the hands of seasoned or specialized characters - they are more mid level, rather than lower.