What True Sight is
An invisible hero can't be seen with ordinary vision — only True Sight reveals them. It's a special type of vision granted by just a few sources: the items Sentry Ward, Dust of Appearance and Gem of True Sight, plus a handful of hero abilities — some of them unlocked or upgraded by Aganim's Scepter and Shard. Without True Sight you can neither see an invisible hero nor target them.
A regular Observer gives vision but does NOT detect invisibility. True Sight comes from Sentry (a spot), Dust (the chase) and Gem (permanent). Cheap detection is a mandatory part of your starting buy against invisible heroes: one well-timed Sentry pays for itself with a whole saved fight.
Sentry Ward
Sentry Ward is the cheapest detection, around 50 gold. It's a stationary ward: you place it on the terrain and it grants True Sight in a radius around itself for as long as it stands. A Sentry lasts 7 minutes and hands out True Sight in a 1050 radius, but gives no terrain vision — it only reveals what's invisible.
- Spot control. Sentries go on rune spots, chokes and the approaches to Roshan so the enemy can't walk in invisible.
- Deny enemy wards. A Sentry reveals enemy Observers — it's the main dewarding tool.
- Paired with an Observer. The Observer gives vision, a Sentry beside it gives detection. Together they cover both "I see" and "I see the invisible".
How to place wards for vision and detection is covered in the warding in Dota 2 guide.
Dust of Appearance
Dust of Appearance is a consumable for 80 gold. Unlike a Sentry, it isn't placed on the ground: it fires with no target, dropping a 1050-radius cloud around you. Invisible enemies caught in it are revealed for 12 seconds, slowed by 20% and take 25 damage on the spot, and the mark lingers another 8 seconds after they leave the cloud. It's a tool for the chase and the fight, not for spot control.
- Catch the runner. Dust reveals and slows an invisible hero trying to escape into stealth.
- Carried in the inventory. A charge or two of Dust on a support or core against an invisible enemy almost always pays off.
- BKB doesn't stop Dust. The Dust mark pierces debuff immunity, so BKB doesn't block it — though activating BKB does strip a mark already on you, since it applies a dispel. What Dust genuinely misses is units hidden by special effects: Slark under Shadow Dance, and anyone under Smoke. That's why the Dust + Sentry combo is kept together.
Gem of True Sight
Gem of True Sight is the most expensive and powerful detection, around 900 gold. While it's in the inventory, the carrier permanently has True Sight around them — no consumables, no timers. But the Gem comes with a risk:
- Drops on death. If the Gem carrier dies, the Gem falls to the ground — and the enemy can pick it up, just like a Divine Rapier.
- Carried by the safest player. Usually the Gem is held by a hero deep in the formation who doesn't dive first.
- Hidden before a risky fight. The Gem can be stashed in base or hidden so you don't gift it to the enemy.
- The Gem has an active. The forgotten half: you can press it, and for 4 seconds it grants True Sight in a 300 radius around the chosen point, showing units and wards even through the Fog of War. Cooldown is 12 seconds, so it doubles as a way to expose an enemy Observer without walking up to it.
How a support finds the gold for a Gem is covered in the GPM and XPM guide.
How and when to detect
Detection isn't "buy it and forget" — it's the habit of reading the game: ferry a Sentry and Dust out by courier in time, and don't walk blind into spots where the enemy might be sitting invisible. That map sense is one of the habits that genuinely raise your MMR.
- React to the pick. If the enemy has an invisible hero, detection in your buy is mandatory from the early minutes.
- Sentries on key spots. Runes, the approaches to Roshan, narrow chokes: that's where an invisible hero is most dangerous.
- Dust for the fight and the chase. Carry a charge to catch up or to deny the escape into stealth.
- Gem when you need permanent detection. Against several invisible heroes one Gem is cheaper than endless consumables.
- Remember Smoke. Smoke of Deceit is not caught by True Sight at all: no Sentry, Gem or Dust will show a team under Smoke. It breaks on its own when a smoked hero comes within 1025 of an enemy hero or tower — so what counters Smoke is not detection but where your heroes and towers sit along the route.
