They've stumbled into the Shrine of Kyuss under the arena and as I'm prepping, of course there are more questions!
1) Room #8 has a glyph of warding "slay living" but Slay Living isn't a thing anymore. Not noted in the conversion. Could be Blight. Or Symbol: Death
2) Room #28 has an Unhallow effect that creates a "Zone of Silence" for non-Kyuss folks. Both of those spells no longer exist, but Hallow has a similar effect with full on silence. Reading the spell description for Zone in v3.5, I'm confused why it's there. People outside the zone can't hear what's in the zone, including sonic attacks. Why would anyone want that? The 5e Hallow version seems better - no sound comes out or goes into the area. So they can't talk to him, but the bard is a lot less effective.
3) Bozal was converted with unholy club (see next question), scroll of Heal and potion of superior healing. Why those items but not the others? Brooch of Shielding seems helpful since he wants to maintain concentration. Periapt of Health appears to be story-driven - protects him from the Kyuss worms!
4) Unholy club is converted to do damage to good creatures, but 5e has moved away from alignment-based effects. Maybe it should be sentient to account for the alignment? Reading the 3.5 unholy weapons, it looks kind of neat. You can use it if you're good, but you're effectively 1 level weaker!
5) Bozal memorized Heroes' Feast? 1,000gp consumed when cast? Is he hosting a big party that night? Same with Feign Death.
6) "True Sight" is actually "True Seeing", and more relevantly, it's a 6th level spell, not 7th.
7) The Channel Divinity power to deal 39 necrotic on an a melee hit seems a bit random. Is it mirroring the "death touch" ability of the original Bozal? Shouldn't it then be 11d6 (39) not straight up 39?...oh wait, it's based on the Death domain in the DMG (p96). That took a while out figure out/find! And explains the extra 2d8 damage with the club that I thought related to it being unholy.
8) Heal over Harm?
9) I was thinking he might want Stone Shape, just to get around the plug to the Ghast area, since they supposed throw a body in there every week.
10) 14 STR gives +2 to attack, but +1 Unholy Club attack shows +2 to hit not +3.
11) Where does the 1/day Hellish Rebuke come from?
The original Bozal has a bunch of summoning to keep PCs busy. But that just doesn't seem available for clerics in 5e. I'm thinking he has Death Ward already cast (Mage Armor for clerics!), and maybe starts with Antilife Shell to keep the melee enemies away. But with his Channel Divinity power, he's almost most dangerous up close, other than having just 1 attack a round and only +3 to hit.