Despite their functional and naming similarities, Divine Challenge and Divine Sanction are quite different.
Divine Challenge is a Paladin class power, minor action, close burst 5, that allows the Paladin to mark an enemy. The mark lasts until this power is used again. The Paladin must engage this target by attacking the target or ending his or her turn adjacent to it or the mark ends. If the target makes an attack that does not include the Paladin, it takes 3/6/9+CHA mod radiant damage.
Divine Sanction is an effect of certain attack powers (such as Ardent Strike) which counts as a mark and, if the target makes an attack that does not include the creature that placed the Divine Sanction, it takes 3/6/9+CHA mod radiant damage. Divine Sanction ends when the power that applies it specifies that it ends.
There are a number of important differences:
- Divine Challenge is a power that applies a mark; Divine Sanction is a mark that is applied by a power.
- You get Divine Challenge by being a Paladin. You can only obtain Divine Challenge by being a Paladin or taking the Soldier of the Faith multiclass feat.
- Divine Challenge (Hybrid) is a slightly different version of Divine Challenge that deals less damage (0/2/4+CHA) and is only available to Hybrid Paladins.
- Note that although Divine Challenge's damage is reduced for Hybrid Paladins, Divine Sanction still deals its full damage.
- Anyone can place Divine Sanction so long as they have a power that places Divine Sanction, even if they are not Paladins. For example, a Half-Elf with Ardent Strike as their Dilettante power can place a Divine Sanction without having the Divine Challenge Power or counting as a Paladin.
- Divine Challenge must be maintained by engaging the target, but Divine Sanction does not have an engagement requirement.
- The Mark applied by Divine Challenge does not need to be re-applied so long as the Paladin engages the target, though the mark ends if the power is used again (ie: on another target).
- Divine Sanction lasts only the duration specified in the power, usually just until the end of the Paladin's next turn (eg: Ardent Strike) though can last longer. Unyielding Faith places a Divine Sanction that lasts until the end of the encounter, for example. Applying Divine Sanction to more than one target does not end existing Sanctions.
- Divine Challenge can normally only target one creature, but Bradaman's Weapon and None Shall Pass (level 12 utility) allows the Divine Challenge to target two creatures in the burst. Celestia's Challenge (level 11 encounter) marks targets as if by Divine Challenge, rather than applying Divine Sanction.