Bigfoot was designed to be a boss. Nexon had a glitch in the BigFoot script, making it a regular monster, that can be affected by Poison Mist, and Shadow Web.
Now, Shadow Web does
Level 1: MP -10; Holds the enemies with 42% success rate for 5 seconds
Level 2: MP -10; Holds the enemies with 44% success rate for 5 seconds
Level 3: MP -10; Holds the enemies with 46% success rate for 5 seconds
Level 4: MP -10; Holds the enemies with 48% success rate for 5 seconds
Level 5: MP -10; Holds the enemies with 50% success rate for 5 seconds
Level 6: MP -10; Holds the enemies with 52% success rate for 6 seconds
Level 7: MP -14; Holds the enemies with 54% success rate for 6 seconds
Level 8: MP -14; Holds the enemies with 56% success rate for 6 seconds
Level 9: MP -14; Holds the enemies with 58% success rate for 6 seconds
Level 10: MP -14; Holds the enemies with 60% success rate for 6 seconds
Level 11: MP -18; Holds the enemies with 62% success rate for 7 seconds
Level 12: MP -18; Holds the enemies with 64% success rate for 7 seconds
Level 13: MP -18; Holds the enemies with 66% success rate for 7 seconds
Level 14: MP -18; Holds the enemies with 68% success rate for 7 seconds
Level 15: MP -18; Holds the enemies with 70% success rate for 7 seconds
Level 16: MP -22; Holds the enemies with 72% success rate for 8 seconds
Level 17: MP -22; Holds the enemies with 74% success rate for 8 seconds
Level 18: MP -22; Holds the enemies with 76% success rate for 8 seconds
Level 19: MP -22; Holds the enemies with 78% success rate for 8 seconds
Level 20: MP -22; Holds the enemies with 80% success rate for 8 seconds
And it does about 33% of it's HP's damage. HP/MP: 32,000,000/ 10,000,000 You do the math. Keep doing shadow web = Ownage. 2.6 Mil EXP.
Times that by two because of the event. 5.2 Mil EXP. Now add a 2x Exp card. Lulwut. :]
