Szadek
* An at-will that drains healing surges and an immediate interrupt that activates when any player does anything other then a basic attack within 10 squares seems a bit brutal. I don't think any MM critter drains or alters healing surges.
Regarding draining healing surges...
A level 15 fighter with 16 con has 115 hit points, so a 26 point healing surge. Thus, in essence, Szadek's at-will 1d10+6, with a secondary attack for another 26 points. If both attacks hit, that's an average of 36.5 damage, though most of that is from losing a healing surge.
A level 15 wizard with 12 con has 78 hp and a 19 point healing surge. Thus, vs. him, Szadek deals 1d10+6 and a secondary attack for another 19. If both attacks hit, that's an average of 29.5 damage, though again most of that is from losing a healing surge.
It's also worth noting that the wizard likely has a good will save and the fighter likely has a good armor class, so it's moderately unlikely that both the primary and secondary attack rolls will hit.
It's also worth noting that draining a healing surge doesn't directly hurt them; it makes them less able to heal, true, but it doesn't make them
need to heal.
(I forgot to adjust these con totals for level up increases, but it won't make a huge difference. But in theory the fighter would probably have around 20-22 con, and the wizard might have 14-16)
By way of comparison, an adult red dragon, level 15 solo soldier, has a single +22 vs. AC attack, with reach 2, which hits for 2d8+7+3d6, an average of 26.5 damage. That's also all damage straight to the HP, which forces the party to heal.
As for Shadow of Doubt, first let me make sure my assumption is right: anyone can only make a single immediate action per round, so Szadek can only use that ability on one PC per round, not use it on every PC every action. Is that correct?
Assuming it is, what that power amounts to is preventing one PC from using his big guns. It doesn't actually steal an action, though, the PC's still free to use another power. A wise PC might even trick Szadek, using encounter powers exclusively until he wastes his shadow of doubt and then using a daily. So really, Shadow of Doubt isn't an outright powerful ability so much as an obstable the players need to learn to play around.
* It doesn't state on syphon psyche who is actually hit in the close burst. Everyone he can see? Everyone in the burst I assume? And is it supposed to be close burst 10 (!)?
It's supposed to be everyone in the burst. See for example the Adult Red Dragon's breath weapon and frightful presence abilities; the breath weapon doesn't specify targets, so it hits everyone. The frightful presence specifies that it hits enemies.
- Sapping claw: Maybe drop the lose a healing surge mechanic and keep the healing? Add daze or immobilize instead?
For the reasons outlined above, I don't think there's any balance problems with this ability. If anything, I'm worried that he might be a bit underpowered; even if he saps all the PCs healing surges, he still doesn't do very much straight out damage on his own.
- Shadow of Doubt: How about a 5-6 recharge ability that stuns someone within 10 squares that strikes him?
As above, I think you overestimate the power of this ability.
- Siphon Psyche: Maybe everyone in close burst 10 takes a +18 vs Will hit with 15 ongoing psychic damage (save ends) and szadek heals 15 for each target affected? If he has some minions around that can be a pretty nice hp regen.
Ongoing 15 psychic damage is more than losing a healing surge to a wizard, and comparable to losing a healing surge to a fighter. On top of that, it's damage straight to their hit point totals, so it's more dangerous.
Grave-Shell Scarab
* Probably wouldn't hurt too much to simplify dredge to be automatic on its next turn. As is, can you stop it from rising somehow and since it will rise at some point what do you do if everything else dies. Do the players stand around waiting for them to pop up? Also, might want to make clear it stands as a move action when it rises (see troll regeneration).
* You can probably just say it rises with 55 hp right in the power description.
He was a tricky one... I kind of like the idea of it rising randomly, but maybe you're right about it being better off to get up immediately. On a side note, I don't think it's such a bad thing if the encounter ends before the scarab rises; Since each minute that passes is 10 rounds, that's 10 chances per minute that it will rise again. If the PCs take an extended rest in the vicinity, that's 50 chances. Personally, I'd probably just handwave it and say that 30 seconds later it rises up.
Gruul horde
* Lob statue?
Kind of specific to the setting. Since Ravnica is a giant city, I don't think it's that hard to believe that one of the bigger guys in the horde could find a statue to rip up and throw at people every few rounds. Of course, large boulders and chunks of masonry work as well, and in a pinch you could even throw the dude next to you.
Elemental Weird
* Cool
Stole the idea from WoW. There are these demons on Hellfire Peninsula called Vacilitating Voidwalkers which start off shooting shadow bolts, but the first spell you hit them with, they start shooting a different kind of bolt of the same type and become highly resistant to that same type. Huge PITA for my Blood Elf paladin to take down, since she's exclusively holy damage, until I learned that the racial Mana Tap ability forced them to convert to Arcane even though it wasn't a spell and didn't damage them.
