Why you should be building Unholy Grail First item.
First off, you should only build it on champions that can utilize it well.
Champs that can utilize it well: 
(ap , W max against a team that has a front line) 
Point 1: It is gold efficient on its own.
Cost Analysis* Gold Value 30 ability power = Gold 652.5 10% cooldown reduction = Gold 266.67 30 magic resistance = Gold 540 100% base mana regeneration = Gold 500 Total Gold Value = Gold 1959.17 Gold Value with Passive Regen
20 ability power = Gold 435 Total Gold Value = Gold 2543.33 Gold Efficiency*
Athene's Unholy Grail item Athene's Unholy Grail is 93.29% gold efficient without its passives, and 114.01% gold efficient after applying the passive ability power passive. Athene's Unholy Grail's gold efficiency is further increased by 5.17% for every 25% mana regeneration obtained from other sources.
Point 2: It makes the rest of your build more efficient
UNIQUE – DISSONANCE: Gain +5 ability power for every additional 25% base mana regeneration. Disables HARMONY on your other items.
By building 
first you are making every other mana regen item you buy more efficient. If your end build looks something like this: 
you will be getting 500% bonus mana regen or 100 free ability power! In terms of gold value that is 2175 free gold in stats!
Point 3: The heal is really nice, is fun to use and feels rewarding.
UNIQUE: Gain 25% of the premitigation damage dealt to champions as Blood Charges, up to 100 - 250 (based on level). Healing or shielding another ally consumes charges equal to 100% of the heal or shield, to heal them, up to the original effect amount.
This is really handy vs poke comps, will keep your team topped off as you siege but also can be really big for saving your adc or other ally. But it actually feels best when used on your tank. Nothing will make the other team cry more than throwing an empowered E on someone like 
. The shield is alone is huge, but now you are healing them for 250-300 HP on top of that.
One thing to keep in mind though when deciding to rush this item is whether or not the opposing comp has someone you can get stacks from. If the enemy team is mainly made up of back line champs, then you will have trouble stacking your . But if the enemy team comp has a tanky front line then you will have no trouble at all stacking. You will be able to chuckle to yourself when 
or some other tank gets picked, because you know it is free stacks for your . is at its best when your team has a tanky front line and so does theirs.
Point 4: The Heal component of combos well with the other support items.
Bonus healing and shielding effects from will be more efficient when paired with . They will not only boost your Champions built in Shield but it will also boost the power of the healing mechanic on the . What was capped at a 250 point heal now becomes a 350 point heal when you have the 40% bonus healing, and that is on top of the shield or heal you are already giving. If the target of your heal/shield also has a 
then it will be even bigger!
I really do believe that is an under appreciated item and is much better than people think. Maybe people just don't like support, maybe people just have not figured it out yet. But I love support and hopefully this build might help other support mains feel more impactful in their games and be able to climb up the ladder as well.
If you want to see it in action you can follow me at: https://www.twitch.tv/commonsatyr. May the climb be ever in your favor.
Oh and remember
Pick smart, Build Smart, Play Smart and you will climb.
