Give Vrondiss indestructible by any method.
Deal damage to Vrondiss.
Vrondiss triggers, creating a 5/4 Dragon Spirit creature token.
The Dragon Spirit enters the battlefield, triggering Scourge of Valkas, causing the Dragon Spirit to deal damage to Vrondiss equal to the number of Dragons you control.
The Dragon Spirit and Vrondiss trigger.
Resolve the Dragon Spirit trigger, causing you to sacrifice it.
Resolve the Vrondiss trigger, creating a 5/4 Dragon Spirit creature token.
Repeat from step 4.

Infinite death triggers

Infinite ETB

Infinite LTB

Infinite sacrifice triggers

Vrondiss, Rage of Ancients

Scourge of Valkas

Cast Rite of Replication with kicker by paying {7}{U}{U}, creating five token copies of Scourge of Valkas.
The five Scourge of Valkas tokens enter the battlefield, triggering each Scourge of Valkas five times.
Resolve all Scourge of Valkas triggers, dealing at least 180 damage divided among a maximum of 30 targets.

Near-infinite damage

Rite of Replication

Activate Orthion's second ability by paying {6}{R}{R}{R} and tapping it, creating five token copies of Scourge of Valkas.
When the Scourge of Valkas tokens enter, each Scourge of Valkas triggers five times.
Resolve all Scourge of Valkas triggers, dealing at least 180 damage divided among a maximum of 30 targets.

Orthion, Hero of Lavabrink

Cast Devastating Onslaught by paying {10}{R}, creating five token copies of Scourge of Valkas.
The five Scourge of Valkas tokens enter the battlefield, triggering each Scourge of Valkas five times.
Resolve all Scourge of Valkas triggers, dealing at least 180 damage divided among a maximum of 30 targets.

Devastating Onslaught

Deal damage to Vrondiss.
Rite of Passage and Vrondiss trigger.
Resolve the Rite of Passage trigger, putting a +1/+1 counter on Vrondiss.
Resolve the Vrondiss trigger, creating a 5/4 Dragon Spirit creature token.
The Dragon Spirit enters the battlefield, triggering Scourge of Valkas, causing the Dragon Spirit to deal damage equal to the number of Dragons you control to any target.
The Dragon Spirit triggers, causing you to sacrifice it.
The Dragon dies, triggering Outpost Siege, dealing 1 damage to Vronidss.
Repeat from step 2.

Infinite damage

Rite of Passage

Outpost Siege

Activate Kiki-Jiki by tapping it, making a token copy of Changeling Berserker.
The token Changeling Berserker and Scourge of Valkas trigger.
Resolve the Changeling Berserker trigger, exiling Kiki-Jiki.
Resolve the Scourge of Valkas trigger, dealing 3 damage to Changeling Berserker, killing it.
The token Changeling Berserker triggers, returning Kiki-Jiki to the battlefield.
Repeat.

Combos with "Scourge of Valkas"