The 'I' in Ian's mouth, naturally, is not himself currently located in Canaan Moore, but rather the 'I' situated on Dragon Island.
The essence of the True Dragon's Spark is essentially a condensed elemental spirit substance, in other words, much like the properties of a Dragon Crystal, it is a material state spirit substance storage device. It can, of course, be placed in the Domain of Void, waiting for others to retrieve it.
However, the person retrieving it must also be powerful; without the ability to materialize the soul, it is impossible to touch it, without the ability to freely leap through the Domain of Void, it is impossible to carry it away.
Coincidentally, Ian now possesses both abilities.
As for why Ian needs the Spark, the answer is simple.
