Power pools are containing four or five related powers that may be selected instead of primary or secondary powers beginning at level 4. Pool powers usually aren't as effective as their cousins in primary and secondary powersets. However, they can be used to cover a weakness in your power sets (Aid Self for an Electric Armor brute), provide support abilities to your team-mates (Assault for a defender), or have a surprising twist or contradiction on your archetype and power sets. This comes at a loss in raw power from dedication to your main powers; the choice is yours.