Ok I was thinking of an mana regen item for tanky champs who have hi mana costs late game and low mana regen so they can stay longer with there team to help in team fights and it also helps give mobility when your low to escape safer from team fights.

chalice of harmony + giants belt 

Feral's Trophy

+400 health

+40 magic resist

+10 mana regen

Unique Passive - mana font:

increases your mana regen

by 1% per 1% health you are missing.

Unique Passive :

when your health drops to 25% of your max health

you gain 30% movment for 2 seconds ( cooldown 60 seconds)

Total cost is 2450 g  

combine cost 150g