With good control, any 5 heroes can kill Roshan before the match begins. It takes a good amount of teamwork and some money spent on health potions, however, and is easily punished if the opposing team realizes it. Because of this, the strategy is rarely seen.
There are certain heroes who are more effective at killing Roshan because of how their abilities work at level 1, and the increased speed or less punishment taken makes level 1 Roshan kills more common when some or multiple of the following are on a team:
- Ursa (Fury Swipes stacks indefinitely)
- Auras (Skeleton King, Luna, Drow, Beastmaster, Shadowfiend)
- Lich (Frost Armor slows Roshan attack)
- Venomancer (Wards can deal damage)
- Vengeful Spirit (Howl reduces armor by 2)
- Viper (Corrosive skin damages and slows attack speed)
- Any summoner plus Enigma. (Beastmaster, Nature's Prophet, Lycan, etc.). You can convert that summon into Eidolons and use further summons to damage, depending on hero.
- Lone Druid
- Wisp (Double effectiveness of Healing Salves with Tether)
- Timbersaw (Reactive Armor)
The reward is significant. Heroes will be halfway to level 3 if all split the experience, or if coordinated well one hero can be the only one within experience range and jump all the way to level 5. Each hero receives 200 gold and the killer gets a gold bounty of between 105-600 bonus gold. And, of course, the Aegis of the Immortal drops.
Items that help:
- Ring of Basilius for the +2 armor aura is an obvious one.
- Healing Salves. You can take turns tanking Roshan and healing quickly thereafter.
- Smoke of Deceit. If you're coming from the Radiant side, you're likely to be spotted without this. It also wears off when the enemy is nearby so you can know if you've been spotted on the way in. It also increases movement speed to get you there faster.
- Stats and regen. You are going to lane after this, and the bonus health and damage helps here too.
It's worth noting that the most popular combo recently is simply Ursa plus Skeleton King. Two coordinated players can kill Roshan by themselves with these heroes. Here's a video walkthrough I made to doing this:
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Although he can attack during the Blade Fury, the attacks do no damage to most targets.
Therefore the ancients don't take damage when you use Blade fury on them because they are magic immune and your physical attacks are doing no damage.
Roshan on the other hand has 75% magic resistance as well as a fair amount of health regeneration, making Blade Fury do minimal damage.
Although Blade Fury doesn't make your physical attacks totally useless while in Blade Fury, if you have an orb effect (a unique attack modifier) such as Eye of Skadi, the slow from the orb will still be applied to them. However, be aware of orbs that are also blocked by magic immunity (such as Chain Lightning from Maelstorm or Mjollnir).
A list of orbs that go through magic immunity:
- Desolator's Corruption
- Eye of Skadi's Cold Attack
- Any lifesteal (although if you're doing no damage this won't really help you)
- Orb of Venom's Poison Attack
And for completeness sake, there are two other orbs that go through magic immunity:
- Lone Druid's Spirit Bear's Entangling Claws
- Ursa'a Fury Swipes
Furthermore, I said that it will make your attacks do no damage against most targets, however there are some exceptions to this. If the target is a structure (towers, Undying's tombstone), mechanical unit (catapults), or a ward, then they will take normal damage as if you weren't in Blade Fury.
Best Answer
Roshan provides several bonuses to the team that kills him:
Roshan spawns at the beginning of the game, and respawns 10 minutes after he was last killed. And he also gets stronger as the game goes on, powering up every 5 minutes.