The Sweet Death is a Mystery Class dragon released on February 27th, 2015. They can be purchased for 750 gems (600 for members) from the store.
From the How to Train Your Dragon Wiki:
- "This deceptive Mystery Class ambusher buries itself and uses its super sweet-scented tongue to lure its prey. If you have a sweet tooth, beware! When the Sweet Death picks a sweet spot in a battle, it usually stays put until its acid attacks win the day.
- "Its tree-like tongue may be a camouflage. Unsuspecting victims may go closer to it to its tongue and it gives the Sweet Death an opportunity to strike. It appears has pink saplings, according to Hiccup. Similar to the Changewing, the Sweet Death shoots highly corrosive acid at its opponents. It is great for achieving offensive and defensive goals, which makes it a dangerous dragon."
For more information on the Sweet Death, visit here.