I'm looking for advice on spell selection and tactics for a 17th level Wizard (CR 18 Worm That Walks) I've been throwing (repeatedly) at my party.
His spell list as it stands is:
9th - time stop, summon monster IX
8th - persistent flesh to stone (DC 25), quickened greater invisibility, mind blank
7th — persistent baleful polymorph (DC 24), quickened fireball (DC 20), mage's sword, reverse gravity
6th — chain lightning (DC 23), cold ice strike (DC 23), persistent confusion (DC 21), disintegrate (DC 25), quickened mirror image, quickened resist energy
5th — overland flight, quickened shield, persistent stinking cloud (DC 20), telekinesis (DC 24), telepathic bond, quickened true strike
4th — acid pit (DC 21), black tentacles, dimension door, fire shield, quickened mirror image, overland flight
3rd — dispel magic (2), fireball (DC 20), haste, hydraulic torrent, protection from energy, spiked pit (DC 20)
2nd — mirror image, pyrotechnics (DC 21), resist energy (2), scorching ray (2), web (DC 19)
1st — grease (DC 18), expeditious retreat, feather fall, hydraulic push, magic missile (3)
0 (at will) — acid splash, light, mage hand, mending, prestidigitation
Opposition Schools Divination, Necromancy
The first two times they encountered him the party was forced to retreat; the third time they eventually whittled him down enough to trigger his contingent Dimension Door, but he'll be back.
He's studied the party carefully and knows the party's tactics (or lack thereof). The party is 16th level and consists of a blasty Cleric (Flame Strike), a blasty Oracle (Chain Lightning), a melee Barb, a melee Monk, an Arcanist, and a Paladin.
He's been fairly successful keeping most of the party locked down using BF control, summons and pits (and Bull Rushing PCs into pits) and enough direct damage to keep the healers busy and if his BP or FtS sticks those need to be healed as well, but the Monk consistently eludes him (Fort 17, Ref 23, Will 19, 32 touch AC), and, in the most recent encounter, was able to (fortified with Resist Energy (Cold) to ignore damage from Fire Shield) eventually force him to retreat.
In the most recent encounter he had prepped Project Image (his Blindsight 30' stays with his meat body allowing him to use both forms quite effectively) and Prismatic Wall (Killed one PC and Plane Shifted another with this), but still just didn't have enough spells to take down all the PCs.
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Basically I'm just looking for new tactics to keep the PC's one their toes the next time they encounter him, and maybe give him a little more staying power.
Oh, and with few exceptions, I'm limiting this guy to the CRB and APG, just so you know.