Can be tamed.
Located in Old Drust Road, Tiragarde Sound. The Guardian of the Spring is normally friendly but can be tamed if you use the toy "N'lyeth, Sliver of N'Zoth" while in War Mode. This version of the Guardian is the one that appears by Roan Berthold near Southwind Station (approx 67,52) for a short time after completing its associated vignette. The original version of the Guardian appears at The Placid Spring (approx 61,52) and can be mounted and ridden for 40 seconds. If you ride it to Roan Berthold at approx you'll be dismounted and receive a lootable chest.