Champions Online has a feature rare to MMORPGs, the ability to block deliberately. While blocking (default key: shift), damage and knockback are greatly reduced and the chance of being held is completely reduced. Blocking also generates energy except in the Avenger and Brawler Roles. This energy gain scales with your Ego, except in the Protector Role in which the energy gain scales with Constitution.
The most common use of blocking in PvE is to defend against "Schtick Attacks", named after comic book "sound effect" bubbles. When a mob begins to charge a powerful attack, a symbol appears over their head; the attack is released when fully charged. Because these are easy to prepare for, and usually contain some kind of hold or knockback in addition to substantial damage, it is usually a good idea to block these attacks.
Blocking can be disabled for 10 seconds in PvP by a power with the Crippling Challenge advantage.
This section lists the blocking abilities that are available from various power sets. These blocking abilities replace the one you automatically start with.