Sarkhan's Ultimate - Attack of the Dragonlords Trigger Guide:

Dragonlords Starting Toughness:
Dragonlord Silumgar = 5
Dragonlord Atarka = 8
Dragonlord Dromoka = 7
Dragonlord Kolaghan = 5
Dragonlord Ojutai = 4
Dromoka, the Eternal = 5
Atarka, World Render = 4
Ojutai, Soul of Winter = 6
Silumgar, the Drifting Death = 7
Kolaghan, the Storm's Fury = 5

Dragonlord Dromoka's Bolster Guide:
Atarka, World Render 6 > Dragonlord Ojutai 6 > Dragonlord Kolaghan 7 > Dragonlord Silumgar 7 > Kolaghan, the Storm's Fury 7 > Dromoka, the Eternal 7 > Ojutai, Soul of Winter 8 > Atarka, World Render 8 > Dragonlord Ojutai 8 > Dragonlord Dromoka 9

Post-Bolster Toughness:
Dragonlord Atarka = 8/8 Trample, 0 counters
Dragonlord Ojutai = 9/7 Hexproof, 4 counters
Dragonlord Kolaghan = 8/7 Haste, grants haste, 2 counters
Dragonlord Silumgar = 5/7 Deathtouch, 2 counters
Dragonlord Dromoka: 7/9 Lifelink, can't be countered, 2 counters
Atarka, World Render = 10/8 Trample, 4 counters
Kolaghan = 6/7, 2 counters
Ojutai = 7/8, 2 counters
Silumgar = 3/7 Hexproof, 0 counter
Dromoka = 7/7, 2 counters

Triggers Upon Attacking:
All dragons receive Bolster 2 by the order stated above, an additional +10/+0, Double strike, a hard-tap on up to 10 non-land permanents and give the defending player's creatures -1/-1 by the number of dragons swinging at him. Your opponents cannot cast spells when Dragonlord Dromoka is put onto the battlefield, and she will lifelink for 17 damage, twice. Dragonlord Atarka deals 5 damage divided as you choose between creatures and planeswalkers. Dragonlord Silumgar gains control of target creature or planeswalker until he is removed. Draognlord Ojutai 'Anticipate's twice when making contact with opponent's face. Dragonlord Kolaghan grants all of them Haste and prevents flashbacking of creatures / planeswalkers.

This kills the opponent.