Normally, the triggered ability on Caged Sun is a mana ability, as it meets the conditions to be a triggered mana ability - it triggers off the activation of a mana ability, doesn't target, and could add mana to a player's mana pool as it resolves.

However, there are situations when Caged Sun won't trigger off a mana ability:

Xenograft naming Saproling
Life and Limb on the field
Deathrite Shaman

Deathrite Shaman is a Land Creature - Forest Elf Shaman Saproling (applying dependencies, which stipulate that Xenograft should be applied before L&L), but its first ability is not a mana ability, as it has a target. It is an ability of a land that is adding mana to the mana pool, so it meets the trigger conditions, but, it would seem that under a strict reading of 605.1b and 605.5a:

605.1b A triggered ability without a target that triggers from activating a mana ability and could put
mana into a player’s mana pool when it resolves is a mana ability.

605.5. Abilities that don’t meet the criteria specified in rules 605.1a–b and spells aren’t mana abilities.

605.5a An ability with a target is not a mana ability, even if it could put mana into a player’s mana
pool when it resolves. The same is true for a triggered ability that could produce mana but
triggers from an event other than activating a mana ability, or a triggered ability that triggers
from activating a mana ability but couldn’t produce mana. These follow the normal rules for
activated or triggered abilities, as appropriate.

Caged Sun's ability should therefore not be treated as a mana ability in this situation.

Confirmation would be appreciated.

Edited Trey Cizek (Jan. 3, 2014 12:21:59 AM)