Abilities/Items that grant vision

Solution 1:

Most of this items/skills can only be used to get temporary vision of small areas,nothing really should extend the default day/night vision of your hero.

Only heroes/items currently in dota 2 are listed.

Invisibility, omnislash, infest and other spells that only displace/change the position of your hero's vision are not included,on the other hand gaining access to inaccessible high ground is included since it prolongs your vision radius significantly and makes ambushes easier even tho you can move.

Items:

• Aghanim's scepter on:

  • Night stalker (Ultimate gives you unrestricted enemy hero vision during night).
  • Keeper of the Light (During daytime, unobstructed vision is granted)

• Obviously, wards.

  • Observer Wards (Provides 1500 radius vision for 7 minutes)

  • Sentry Wards (Provides truesight in a 850 radius for 4 minutes (Can see invisible units/enemy wards) and regular vision in a 150 radius for 12 seconds)

• Using Courier as scout, especially upgraded (flying). It's risky and rarely done, but possible.

• Blink Dagger blinking on inaccessible high ground gets you more vision (rarely useful since you can't move).

• Manta Style 2 illusions gets you 2 more points of view.

• Helm of the Dominator using dominated unit as scout.

• Necromonicon 2 scouts 2 more points of view. The level 3 melee Necronomicon unit has true sight.

Heroes:

• Beastmaster boar and hawk companions can be used as scouts. The hawk can turn invisible at level 3 and be used as a ward fairly effectively, especially since it has flying vision.

• Invoker

  • Tornado vision along the path.

  • Defeating blast vision along the path.

  • Sun strike reveals the area it will hit before the damage impact.

• Clockwerk Rocket Flare gives you vision during the path + few seconds on the area they explode. If timed correctly, rocket flare can block creep camps.

• Slardar Amplify Damage gives you vision around the target enemy and provides truesight of the enemies it is on (Not in AoE).

• Lich Chain Frost gives you vision as it bounces from targets.

• Dazzle Weave prolongs vision towards affected targets. Also provides 800 radius flying vision of the area it's on.

• Spirit Breaker Small area around the charged enemy is revealed and the map you charge over is revealed during the charge. The target remains targeted, even if invisible, and a silhouette is visible. However, the target is not selectable without some other form of truesight.

• Crystal maiden Frost nova reveals AoE at target area (due to short cast range only portion of it is useful).

• Lycanthrope Your invisible wolves are very good scouting units.

• Jakiro

  • Ice path Reveals area around the path (can reveal high ground).

  • Macropyre Reveals area where cast and it keeps the vision during the afterburn.

• Vengeful Spirit Wave of terror reveals area in targeted direction.

• Anti-Mage access inaccessible high ground with blink.

• Weaver Swarm grants vision along path, reveals the high ground also. If a bug attaches to a unit, vision is granted in a small area around the bug until either it or the unit it's attached to dies.

• Morphling scouting with mirrored unit (Replicate).

• Spectre

  • Haunt creates illusions around all enemies granting you short 5 points of view.

  • Spectral dagger reveals area along path, can get you to inaccessible high ground.

• Mirana Sacred Arrow reveals terrain on its path.

• Witch doctor area around Death Ward is revealed, due the cast range only small part of vision is useful.

• Windranger Powershot reveals area along the path.

• Kunkka

  • Ghost ship gives vision along path + collision radius.

  • Torrent gives you high ground vision of targeted location when it hits.

• Bloodseeker Thirst gets you vision around enemies with low HP (if inside the required radius of you determined by thirst).

• Broodmother your webs reveal terrain where they are placed.

• Queen of Pain access inaccessible high ground with blink.

• Pugna small area where nether ward is placed.

• Bounty hunter Track reveals area around targeted enemy and reveals invisibility of units it is on.

• Lone druid use bear as scout.

• Storm spirit

  • Static remanent reveals small area where it is placed.

  • Ball lightning access to inaccessible high ground.

• Tiny tossing friendly units gets you higher ground vision.

• Razor

  • Static link can be cast at target location and it will give vision along path and reveal the targeted area for 2 seconds in addition it has high ground vision.

  • Plasma field reveals units in its wake.

• Zeus

  • Lightning Bolt reveals small area around the target, revealed area gets truesight.

  • Thundergod's Wrath reveals all enemies on the map and small area with them for a second(hits invisible units and reveals them for the period).

• Puck the Illusory Orb reveals terrain on its path

• Chen persuaded units can be used as scouts.

• Enigma Eidolons as scouts.

• Shadow Shaman Serpent Wards reveal area around them.

• Enchantress can tame units for scouts.

• Dark seer Wall of Replica creates illusions that can be controlled as scouts.

• Warlock vision around summoned Golems.

• Shadow demon 2 controllable illusions and shadow poison, which gives vision of where it travels (goes over the high ground)

• Venomancer plague wards grant you vision where they are placed(useful if placed on high ground).

• Batrider

  • Firefly grants flying vision

  • Firebomb grants vision along path and at targeted area (can be cast on high ground).

• Ancient Apparition

  • Ice blast gives vision as it travels and of the AoE where it hits.

  • Ice vortex also reveals the area it is cast on.

• Nature's Prophet can use his summoned treants as scouts.

• Keeper of the Light Illuminate provides flying vision ahead of the keeper, with the range extending outwards as he channels.

Note while controling neutral creeps.

• Wilkdin can cast tornado that reveals path to its destination.
• Dark troll warlord can summon 2 additional units for scouting.

Solution 2:

This should be pretty much everything, I tested the few that I wasn't sure on but I probably hit most.

Spells that provide temporary flying vision:

• Tiny's Toss
• Kunkka's Torrent
• Night Stalker's Darkness (with Aghanim's Scepter)
• Razor's Static Link
• Batrider's Firefly
• Dark Seer's Wall of Replica

Spells that give vision as they traverse/land:

• Clockwerk's Rocket
• Juggernaut's Omnislash
• Mirana's Sacred Arrow
• Vengeful Spirit's Wave of Terror
• Razor's Plasma Field (unique in that it only grants vision of units, not the area)
• Weaver's The Swarm
• Crystal Maiden's Nova
• Puck's Illusory Orb
• Storm Spirit's Static Remnant
• Windrunner's Powershot
• Zeus's Lightning Bolt (Grants Truesight)
• Shadow Shaman's Mass Serpent Wards
• Jakiro's Ice Blast
• Witch Doctor's Death Ward
• Death Prophet's Exorcism
• Pugna's Nether Ward
• Dazzle's Weave
• Batrider's Flamebreak
• Ancient Apparition's Ice Vortex
• Ancient Apparition's Ice Blast
• Invoker's Sun Strike
• Invoker's Tornado
• Invoker's Deafening Blast
• Bane's Fiend's Grip

• Shadow Demon's Shadow Poison

• Wildkin's Cyclone (neutral creep)

Spells that give vision of affected targets:

• Slardar's Amplify Damage (Grants Truesight)
• Lifestealer's Infest
• Spiritbreaker's Charge of Darkness (Grants Truesight)
• Bounty Hunter's Track (Grants Truesight)
• Bloodseeker's Thirst (Grants Truesight)
• Razor's Static Link
• Spectre's Haunt
• Zeus's Thundergod's Wrath

Items that provide vision:

• Observer Wards
• Sentry Wards (Grants Truesight)

I've ignored summons as all summons will of course grant vision, and I've ignored spells that move you along with them, as it's you providing the vision, not the spell. As you can see, most support heroes have a spell that provides vision of an area. This is to allow them to counterward more easily.