(no subject)
52 AC w/o hacks! Here's how
Level 20 Knight (PHB2)
16 Dex
Base AC - 10
Dexterity Bous - 3
+5 Mithral Full Plate - 13
+5 Large Steel Shield - 7
+5 Amulet of Natural Armor - 5
+5 Ring of Protection - 5
+5 Defending weapon - 5
Dodge Bonus (Feat) - 1
Shield Block (Class Ability) - 3
Total: 52
The AC increasing Ioun Stone won't make any difference, it's a deflection bonus, same as the ring of protection, so they don't stack.
If you get the full plate with the Heavy Fortification enhancement (+5 market price) then you are not susceptible to critical hits, sneak attacks, etc.
Level 20 Knight (PHB2)
16 Dex
Base AC - 10
Dexterity Bous - 3
+5 Mithral Full Plate - 13
+5 Large Steel Shield - 7
+5 Amulet of Natural Armor - 5
+5 Ring of Protection - 5
+5 Defending weapon - 5
Dodge Bonus (Feat) - 1
Shield Block (Class Ability) - 3
Total: 52
The AC increasing Ioun Stone won't make any difference, it's a deflection bonus, same as the ring of protection, so they don't stack.
If you get the full plate with the Heavy Fortification enhancement (+5 market price) then you are not susceptible to critical hits, sneak attacks, etc.