Kog'maw shreds through people with his since it has the added %of max health damage. Both and add on hit damage with each auto making them great additions. is especially good when you get red buff since it doubles the on hit effects. First go for for the life steal. Followed by for the increased targets, thus maximizing damage and to multiple enemies, along with increasing attack speed. For boots are best for the increased attack speed though it doesn't give as much movement speed. Finally adding both and for increased sustain. The also brings your AP up to over 100 so that your does 1% more of enemy max health. You can use if you are facing a high magic resist team and want a little more on-hit damage.