This one is quite common, so I won't mark the post as (NSFW) like I did with hard support Medusa / TB.
This one is also a pure theorycraft and I haven't tried this yet, but Venomancer's new % based ulti makes him an IDEAL counter to magic damage enemy teams, and specifically magic damage enemy teams.
As an offlaner ideally you're picking to be able to hold enemy attention, and provide vision for your team in the fight, acting as a 'front-liner' to some extent.
The problem ofcourse is venomancer has 2.1 strength gain per level. For perspective, DP has 3.0, and Tiny has 4.0. So by later levels Tiny and DP will have almost TWICE the HP of venomancer.
So how do we work around this? Obviously buy strength items, but the problem is venomancer also needs armour to be tanky. Buying armour, AND strength items, AND whatever else you need to buy is too expenive.
– Eternal Shroud
– Thats it, maybe aghs, maybe blink.
The idea is you are attempting to abuse the % based damage of the venomancer ulti, with the shroud's magic lifesteal amp, + the bloodstone's lifesteal amp + veno's talent, + the bloodstone's active, + the magic amp itself, in order to 'compensate' for a low HP pool.
So with this build you get:
Spell Lifesteal = (12% + 15% + 20%) * 30% amp = 61%
Spell amp = 8%
Mathematically, If you hit 5 heroes with your veno ulti in a teamfight, assuming they have 2k hp each. That's 230HP per second of healing, not counting creeps and such, or healing from the gale, which might add another 100hp/s if you do it in a creepwave. This healing persists for 20-25 seconds! (If you hit meepo, you may just become invincible for 25 seconds).
Throw on the bloodstone's active and you've basically solved the HP issues with venomancer offlane. The problem though is armour. There is no way to solve this and still have enough money to buy the other two items as a 'decent' offlaner as opposed to an afk farmer.
Which is why this build ONLY works against magic damage enemies. Because against magic damage enemies, your eternal shroud is already providing a 25% reduction. So you've got 50% magic damage reduction PLUS, insane healing allowing you to basically walk into 4-5 of them, ulti, and begin to dance and survive long enough that if they focus you, they will lose the teamfight to the remainder of your team.