Now, I see nothing in the cards stating you can't have both at the same time, though I might be wrong. Here's the thing--doing the math, if one had both active, you stand to gain quite a lot for losing a little. Just to make sure I'm seeing this right, if you have both Third Eye and Inner Beast active at the same time you get:
One Extra movement point.
+2 to Horror Checks
+2 to Combat Checks
Immunity to Curses
-1 to Stamina
-1 to Sanity
They seem like these cards are supposed to be opposing forces but, like I said, I see nothing saying both can't be active at once. So, is this a viable thing? I mean, would you, a player, be willing to use both, despite the cost to Sanity and Stamina for all that you gain?