Xebec was looking for two abilities in particular
One was in Elbaf, so 100% it is the dragon of Loki.
And reason why Xebec wanted Harald on his side is because he knew only ancient giant like Harald can get the most out of the dragon size.
How would this help the plans of Xebec? I imagine his goal was to take down the red line. Such a island sized dragon along with a other power Xebec had, the gura no mi of WB, that has power to destroy world.
Gura no mi conbined with ancient giant eating the island sized dragon are strong enough to take down the world surrounding red line mountain.
Then you create all blue and Marijois, new marineford is over.

One was in Elbaf, so 100% it is the dragon of Loki.
And reason why Xebec wanted Harald on his side is because he knew only ancient giant like Harald can get the most out of the dragon size.
How would this help the plans of Xebec? I imagine his goal was to take down the red line. Such a island sized dragon along with a other power Xebec had, the gura no mi of WB, that has power to destroy world.
Gura no mi conbined with ancient giant eating the island sized dragon are strong enough to take down the world surrounding red line mountain.
Then you create all blue and Marijois, new marineford is over.
