Argentavis is a ranged and magic boss with two mechanics that stop the fight cold if you ignore them. Neither is hard once you know what to do, but both will waste your whole trip if you do not.

Get there with ::arg or ::argentavis. It can also be instanced.

Basic attacks

Argentavis attacks with either ranged or magic. It sticks with the same style most of the time and switches roughly one attack in four, so it is worth praying against whichever style it is currently using rather than ignoring prayer entirely.

The important detail: the basic attack hits every player in the area at once, not just its target. If you are anywhere in the room you are taking damage, even if the boss is facing someone else.

You cannot safespot it

Its aggression and attack range are both 32 tiles, which covers the entire room. There is no corner to stand in and no distance that puts you out of reach. Plan to tank the damage rather than avoid it.

The minion lockout

This is the mechanic that catches everyone.

Roughly one attack in ten, Argentavis spawns minions. One minion per player in the area, each targeting a different player. While any minion is alive, Argentavis takes no damage. If you attack it you get:

You must kill all the minions before attacking the Argentavis again!

What to do

Switch to the minions the moment they spawn.
Kill all of them, not just yours. The lockout does not lift until every minion is dead.
Go back to the boss.

The minion spawn has a 90 second cooldown, so once you have cleared them you have a decent window of uninterrupted damage before it happens again.

In a group this is faster, since there are more players killing minions, but there are also more minions. It roughly balances out. Solo you only ever face one minion at a time, which makes solo Argentavis considerably simpler than the group version.

If the minions somehow cannot be killed, the lockout lifts on its own after about 18 seconds as a failsafe. Do not rely on it, but it does mean a stuck minion will not end your trip.

Tornados

Also roughly one attack in ten, Argentavis summons a tornado for each player. The tornado spawns within a few tiles of you and then chases you.

It deals 10 to 17 damage whenever it is within one tile of you
It lasts about 11 seconds before disappearing
The special has a 60 second cooldown

What to do

Keep moving. The tornado walks at your speed, so standing still means eating a hit roughly every tick it is adjacent to you. Run laps around the room and it will trail behind you without connecting. You can keep attacking the boss while moving as long as you stay in range, which is easy given the 32 tile range.

Do not try to outrun it to a corner. Just keep circling.

Putting it together

Attack the boss normally, praying against its current style.
Minions spawn → stop, kill every minion, resume.
Tornado spawns → keep attacking, but keep walking.
Heal through the constant basic attack chip damage.

The two specials share nothing, so you can get a tornado while minions are up. If that happens, kill minions while moving. Minions are the priority because they stop your damage entirely.

What to bring

Ranged or magic. The fight is at distance and you need to keep moving during tornados.
Protection prayers. Unlike some bosses, the style here is sticky enough to be worth praying against.
Fast switching to minions. Anything that clears the minions quickly is worth more than raw boss damage, because the lockout is where your time goes.
Food. The area-wide basic attack means constant incoming damage with no way to avoid it.

Speed tasks

The game tracks how long your kill takes, and there is a combat achievement for a fast Argentavis kill. The clock starts on the first attack, so the way to improve your time is to reduce time spent locked out: kill minions fast and never stop attacking during tornados.

Doing it in an instance removes other players from the equation, which means one minion per spawn instead of several. That is the single biggest thing you can do for the speed task.

Related

Awwgentavis is the pet, and gives +2% Ranged experience while out. The Argentavis feather is also the catalyst for Heroic gloves, so kills here feed directly into the endgame glove upgrade. See the Upgrade Recipes guide.