Basic build is outlined below.
Alternate racial trait Arcane Focus.
Class Wizard 20
archtype spell sage
Signature Spell Black Tentacles
Magical linage Black Tentacles
1: Combat Casting
3: Spell Focus Conjuration
5: Spell Focus Divination
Wizard: Heighten Spell
7: Spell Specialization Black Tentacles
9: Mages Tattoo (Conjuration)
11: Steward of the great beyond (arcane discovery)
13: Spell perfection Black Tentacles (via retraining after 20)
Wizard: Widen Spell
17: Augment Summoning
19: True Name
Wizard: Quicken Spell
He would have several instances of Quickened widened Black tentacles prepared, which would be level 7 spells with spell perfection and magical linage.
+5 Adamantine Haramaki of spell Dodging (total effective bonus of 7)
Ring of Freedom of Movement
Belt of stoneskin
Headband of vast intellect + 6
+5 Mithril buckler of spell turning
Ring of Protection +5
Amulet of Natural Armor + 5
orange prism ioun stone
His opening move of combat is to cast a quickened widened black tentacles on himself, cast time stop, cast spellbane (antimagic field, disjunction, greater dispel magic, freedom of movement) and spell bane (dimensional anchor, dimensional lock, disintegrate, and shield)
If he gets more than two rounds out of timestop he casts other buff spells on himself. On his next turn he uses his otherworldly Kimono on the most heavily armored target in the group, then spams spells starting with his lowest level attack spells until he either dies, kills the enemy, or survives getting to 40 hp (in which case his contingency'd teleport goes off).
The key portion of his build is maximizing the caster level of black tentacles. Do to spell specialization, mages tattoo and arithmancy, he is getting a + 4 to the caster level from these feats, which would be doubled to eight from spell perfection, he can add +4 from the archtype ability, the ioun stone adds one, and his trait signature spell also adds one, bringing his caster level for the spell to 34, which gives black tentacles a + 39 on its CMB checks to grapple. Since he disabled freedom of movement via spellbane, unless the party have rings of freedom of movement, or a freedom domain cleric, this should be able to grapple all but the full BAB martial characters.
The easiest way for him to be shut down is for the party to cast their own spellbane which would include spellbane as one of the forbidden spells, this could even be done from a scroll.
The party will have some advance knowledge of the wizards tactics, though how much will depend on them.
Do you have any suggestions or perhaps any ways to further boost black tentacles via magic items?