Not Updated For Current Season
The masteries shown here are not yet updated for the current season, the guide author needs to set up the new masteries. As such, they will be different than the masteries you see in-game.
This build gives you the ability to heal for outrageous amounts. The down side is that there is no mana buffing items, this can be overcome though with infuse.
-No Focus on Mana
This is the build order I prefer because it allows me after I get my Mejai's Soulstealer to be able to continue getting ability power through ***its. These ***its really add up because if you heal another champion or infuse him, you will get an assist if he kills an enemy champion within a short amount of time. Ionian Boots + Morellos allows you to hit max cool down reduction reducing your heal to a 6 sec cool down. Rabadons help out with delivering big heals, which can save your teammates in a pinch. Lastly Abyssal Scepter gives you some survivability and ability power.