Last night on Seventh Hammer I managed to get this with help from my guild. There wasn't many people in my group that could use it, or had better, so I was only rolling against one other person.
In my opinion it's better than a Crystal Chitin Shield and not because it has more AC. WIS creates 12 mana for every below 200 point. After 200 it starts only giving you six, let's add it up...
Skull Marked Shield
Before 200 Wis
84 Wis Mana || 50 added mana || 134 total mana
22 AC || 50 HP
Crystal Chitin Shield
Before 200 Wis
108 wis mana || 40 added mana || 148 total mana
20 AC
Skull Marked Shield
After 200 Wis
42 Wis mana || 50 added mana || 92 total mana
22 AC || 50 HP
Crystal Chitin Shield
After 200 Wis
54 wis mana || 40 added mana || 94 total mana
20 AC
As you can see, the CCS adds more mana in both cases, but after 200 it only adds two more, now what can you cast with two mana? In that case, what can you cast with the 14 extra mana from before? I chose the HP/AC, keep my Druid from getting whacked when he's not looking. (I'm never looking. o.-
Edited, Sun Feb 23 03:58:48 2003