Mephisto by HotSFanfan

Upon taking damage from Mephisto, enemy heroes no longer share vision with their team for 5 seconds.

This means losing shared vision with allied heroes, minions, mercenaries and buildings. The sight range is not affected. Mephisto's signature ability is to spread mistrust.

60 Mana.
5 second cooldown.

Summons a corrupted council member to follow an allied hero, healing them for a moderate amount every 1.5 seconds. Lasts 10 seconds. Multiple council members can follow the same target, increase the heal they receive.

Council member has a health pool and can be killed by enemy heroes to stop the healing. Council members will disappear when their target reaches full health.

In Diablo 2, Mephisto cannot heal himself, but surrounds himself with several monster types that can heal (cantors, council members, blood lords).

50 mana.
12 second cooldown.

Shrouds a target in a cloud of poison for 6 seconds, causing nearby enemies to take damage each second. If the target is an allied hero, that hero will be considered hidden by brush until they attack or use an ability.

The hidden ally will become untargetable for enemies, but can be damaged via skill shots and area effects. The poison cloud is always visible, so this ability is not for stealthing allies, but to make them unclickable. Damage dealt by Poison Shroud is considered Mephisto's damage, so it triggers your trait.

Poison Nova is stolen by Xul.

50 mana.
10 second cooldown.

Throws a frozen missile towards targeted area that implodes, dealing heavy damage and pulling all enemies hit towards the centre of the impact.

Tychus' grenade but with a pull instead.

Signature number one player hero killer in the game.

100 mana.
60 second cooldown. Global ability.

Every second for the next 5 seconds, condemned souls will rise out of the ground in front of all enemy heroes and strike them for a small amount of damage.

Condemned souls have a collision size and will always rise directly in front of the enemy hero. They will disappear again after making one attack. This global ultimate greatly hinders enemy movement, and spreads your trait.

In Diablo 2, evil souls will periodically appear in Mephisto's area and strike your character. Their damage could stun you.

60 mana.
90 second cooldown. Targeted ability.

Mephisto corrupts the soul of targeted enemy hero with hatred. For the next 5 seconds, that target will become hostile towards their own team.

This ability could stop an enemy diver, prevent a heal, or hinder an enemy from escaping towards their fortifications. Does not alter player control in any way, but unwary players might get CC'd or nuked by their own team, or obliterate their own team via friendly fire.