Chrysos the Vain is the blue dragon in Stronghold Dragonflight. He puts a mark on the tank that does 638.4k damage every second (Thunder Spike, pre-mitigation; ~380k to the tank) and does 160k AoE damage when the target dies. The mark hits 30 times and doesn't seem to be dispellable.
This attack hits harder than Halaster in ToMM. It is not telegraphed in any way and instantly appears while the dragon is casting other powers, so you can't prepare for it.
Please reduce the damage from ticks and telegraph the attack.