This comp uses the Jeweled Gauntlet interaction with Vayne to deal lots of true damage to enemy teams. The comp finishes at level 9 with the addition of Nautilus to provide Ironclad.
Go for this comp if you have good Vayne items and have a good Forgotten start.
Level up to 4 early if you want to start a win streak. Level up to 5 to try and continue the streak.
If you're weak in the early game, you can opt to save gold and lose streak instead.
At Round 2, level up to 6 regardless of your start. Put together the strongest team you can.
At Round 1, level up to 7. Roll down to stabilize your comp if you are weak. Afterward, save up to hit level 8 and complete your comp.
Don't focus only on Vayne items. If you can build other Shadow items on other Forgotten units, you can get a nice stat bonus for your Forgotten units.
Zeke's Bleak Herald