first the heilmth:
now every one sayes that [Nidus] no way to helmith him but theres one helmith that can change him the one that help his cc his weakest point i put ensnare because larva cant put it on linked enemise or recast it but ensnare does all of that

second the mods:
[Growing Power] in the aura becasue as much you give [Nidus] strenght he will need more so this helps out, [Primed Sure Footed] because knockdowns can get you killed and interrupt you from dealing damage so this helps out, umbral instentfy and vitalty for health and strenght and beacuse i used the umbral ones i will get bouns health and strenght, [Primed Flow] for energy capacity increase without this mod alot of the energy that you will get from hunter abrenaline and his first huge amount that will go for nothing, [Stretch] for range but i dont need it exept for his first because enemys will not be stacked but they will be beside each other to hit all of them, [Blind Rage] for effecnsy decrase because if you hit for enemys his first will be free cast and if you hit more you will get more than you will lose and of corse for the strenght plus without this mod you will get little amount when you hit more than 4 enemies, lastly adaptition and [Rolling Guard], adaptition because i dont want my linked target to die so this helps out, [Rolling Guard] now most of you will find this silly but look, i have damge defliction from his third i have unlimated healind from his last and damge radiction from adaptition, and you are already undying with his passive so how we about adding invarabilty to him and this buy me more time when my 5 seconds of invarbilty from undying with [Rolling Guard] so you will get more time to heal

third some edition you can run on this build:
if you dont like ensnare idea make it larva and swap [Stretch] to [Primed Continuity] thats if you want to keep [Rolling Guard] but without ensanre if you dont want both of them instade swap his [Rolling Guard] to [Primed Continuity] and keep [Stretch]

fourth arcanes
arcane [Guardian] for armor buff and avenger since you are nothing but health this helps out and you will be pleased with the crits you will deal why not strike becasue i dont like to bring slow weapons that strike to help it

lastly sirvive ablity and how to play this build:
now sirviving is easy with [Nidus] fist always make sure make your third and last are active plus make sure that your stacks are above 70 always use ensnare on linked target if you want to build stacks if not chose any enemy that is near alot of other enemys check my viral king build and the slasher of [Nidus] build