Yeah, that only needs Con 24, which is not too hard. If he started with a 16 and has a toad familiar, he only needs a +4 item.wraith8 said:He has +7 con, and is level 18. 18 x 7 =126 so he has 54 hp from 18d4. Its a high value but still doable
However, the item and familiar bonuses both go away in an antimagic field. Dropping his Con from 24 to 16 would reduce his bonus by 4, meaning an instant loss of (18 x 4)=72 hit points. That's better than most of your attack spells can do in one round. =B^)