AP Rammus, do it.
Build
Morello's evil tome -> Sorc Boots -> Deathcap -> Void Staff -> Archangel -> Rylai's
Do it, power ball like a champ.
Edit: For Shen build
Hextech Gunblade -> Haunting Guise -> Beserk Greaves -> Nashor's - > Rod of Ages -> Rylai's
Build
Morello's evil tome -> Sorc Boots -> Deathcap -> Void Staff -> Archangel -> Rylai's
Do it, power ball like a champ.
Edit: For Shen build
Hextech Gunblade -> Haunting Guise -> Beserk Greaves -> Nashor's - > Rod of Ages -> Rylai's