Quote Originally Posted by Light Mage
Is Death Force the skill you learn from the Adamantioses on Wutai Beach?
Adamantaimai, but yes, on the Wutai beaches.

As BG-57 has said Death Force protects against Death attacks such as Roulette, but it also protects against Lv4/5 Death and the Master Tonberry's Knife attack. However, if you have a party of three against the Master Tonberry Death Force will only work for a single character at any one time, so you need to cast it when you can determine who is going to be Knifed.