Rehgar is a mobile and incredibly powerful support Hero. His chain heal is incredible and as the game goes on, your healing potential gets strong and stronger. Ghost Wolf allows him to quickly get in and out of fights while his Lightning Shield can offer a considerable damage boost. He's my favourite support Hero.

Pros:
Amazing healing power late game that can keep any team alive
Gets rediculously powerful late game due to his full heal and shielding
Your totem is great for coordinating spikes to prevent players escaping

Contras:
Mana hungry early game
Can be focused to prevent him using heals and/or Ghost Wolf
His melee playstyle leaves you vulnerable
He lacks some of Brightwing's utility

Ancestral Build
The talent taken 9/10 times when you will be playing, its a super heal of sort. After a short delay of 1 - 1.5 seconds you will heal your target to full HP (most of the time) and its great, you can bait out so many fights and have the enemy overextend cause of this.

Bloodlust Build
I been playing alot latley with taking this talent, its so much fun to use and it increases your entire teams dmg by so much, its a long duration of 10seconds. But taking this you will loose out on so usally you do this when you got 2 supports on your team or you feeling frisky cause its a super fun ultimate.