Kozilek's Unsealing's triggered abilities trigger before the spell that causes it to trigger
2019-01-25 If a creature entering the battlefield has riot but can't have a +1/+1 counter put onto it, it gains haste
The real hope though is you have 3 or 4 other Titans out, you quest with him and then use Hades - Hotheaded Ruler to ready him and quest it again
That being said you could definitely hook up: Nalia de'Arnise + Edgewalker + Orah, Skyclave Hierophant + Phyrexian Altar So you could potentially keep casting Clerics off the top, sacrificing them for mana, returning them to your hand, recasting and saccing, recurring and creating death triggers, and just generally going nuts
This price point was largely thanks to the immense amount of supply that was readily available on TCGplayer
If the target creature is an illegal target by the time Turn to Slag tries to resolve, the spell won't resolve