"It's most likely the second and third reasons..."
Since using one's own life energy as the cost for casting spells, the wizards of the Life Court would essentially be using "life" for combat, which seems quite unlikely.
"The heritage of the Life Court may be of help to me; if I could increase the total amount of life energy through other means, the battle power of the [Pure Body] Full Giant Demon Transformation could also be enhanced..."
Ronan wanted to improve the combat power of the [Pure Body] Complete Giant Demonization form by not only optimizing the efficiency of the existing life energy utilization but also increasing the base amount of life energy.
If both aspects could be enhanced, that would naturally be ideal.
The Life Court and Ronan pursue two different paths in the use of life energy; the former uses life energy as the driver for Wizard Spells, while Ronan applies life energy directly to himself.
