Where to find and kill unalerted tusk ballistas for riven requirements. Very simple.

Some Riven mods require you to kill a certain number of tusk ballistas with a variety of secondary requirements. Like me, if you have never deliberately searched for them, you'll find that it's quite the challenge once you set out to do so. You will go up and down the plains only finding one at best after wasting a fairly large amount of time. However they're easy to find as long as you know where to look for. But since before the Riven requirements only the most observant would know where are they.

So lets start

Location-Much like all tusks, tusk ballistas can be found on the plains of eidolon. More specifically on guard towers in grineer bases. You are guaranteed one ballista per tower, but if you're lucky you might get two.

Takedown of two ballistas-As far as I know, Rivens require the kill of unaware tusk ballistas. Simple. But when there are two of them on a tower and you want both, you better time your kills correctly so they are not within each other's view. You will also need to be quick before the second one moves and sees her dead comrade.

Equipment-For having the easiest time completing this task, a powerhouse sniper riffle with a hush mod is a given. Nice bonuses will be as much enemy radar you can get and a stealthy warframe.

This is it. Go out there and hunt some tusk ballistas.

[Vanilla Nilla]

I usually go in plains, grab my archwing and then use a sniper with 'hush' mod

[OlekK]

https://ibb.co/Hh1xyrC
https://ibb.co/1RH1CM4

[Nitte]

Just find a decent semi auto and grab anyone who can use a invisible move and you can simply go as close as possible for a ez headshot

[Draegan]

Using a sniper rifle while flying high in an archwing at spawning distance is valid too as it's quicker and maybe harder than stealth approches

[Leo]

Equinox, Ivara and Baruuk can all put the Ballistas to sleep, allowing for easy execution without alerting them.

[Vierynbryn]

one of the things i found works well here is a loki with the invisibility augment, so i can get close if i need to, or i can kill both without alerting the other with a gunshot. takes some time to get around, but thats not too difficult. i also found if you cannot execute a melee stealth attack, they are alerted to some degree, and thus wont count