Ok, before you proceed reading this, you must know this.
You must be on the quest "What Came First, the Drake or the Egg?" (Obtained in Toshley's Station.)
Ok I thought this was an interesting bug/exploit, so check it out.
1. Travel to the Singing Ridge south of Toshley's Station.
2. Clear an area around a Nether Drake Egg and open it.
3. When a whelp comes out, use the Temporal Phase Modifier from the quest on the Nether Drake Whelp. It should transform into one of the following:
-Proto-Nether Drake
-Adolescent Nether Drake
-Mature Nether Drake
*Note this transform takes approx 2-3 seconds, and this is where the bug comes in*
4. DPS your newly transformed mob down to anywhere from 1-40% and begin to transform them.
5. Once you complete the cast, kill the mob before it transforms.
If this is done correctly, you will get full XP for the kill, and another creature which you transformed will also spawn, at whatever HP you transformed that. Please note you don't receive double loot, but you do receive double XP, and you get the loot of the most recent transformed mob.
Sorry if this has been posted before or is confusing, just trying to help.