Leaf of Vitality
From EZ Server Wiki
The Leaf of Vitality is a HP aug that fits on all armor types that have type 24 slots. Unlike many other combines on the server, each level requires only 1 Leaf of Vitality to go to the next level, for example to go from Leaf of Vitality III to IV, you combine the III with a single Leaf of Vitality. The maximum level of each Leaf is 10, which gives 25,000 HP.
1+1=2 then 2+1=3 then 3+1=4 so on and so until level 10