The Baleful swamp lies just beyond Dismal Falls which is along the River of Poisons. The water is deadly poisonous if swallowed as Lion-O explained to Snarfer and Wilykit just before falling in. And Lynx-O warned them that the mists were deadly as well.
The Totem of Dera is one of the treasures of Thundera. It is a healing device used to heal ThunderCats. But it can also bring inanimate objects to life. This is how it can be used as a weapon against the ThunderCats.
(The Mutants approach the unconscious Lion-O)
Vultureman: Well, well. An itty-bitty ThunderKitty.
Wilykit: (holding the Sword of Omens) Stand back! Or...
Jackalman: Or what, pipsqueak?
Lion-O: As usual, Mutants, you're very brave when it's three against one. But when the odds are even, you're just a bunch of cowards.
Monkian: Are we gonna let him talk to us like that?
Jaga: You may not be able to see me, Snarfer, (wraps cloak around Snarfer) but concentrate. Hear my thoughts and I will tell you what to do. Listen.
Jaga: The weapon Vultureman used, the Totem of Dera, the most magical and ancient of our ThunderCat treasures, that is the only hope of saving Lion-O!
Wilykit: Snarfer? What is it?
Snarfer: It... It... It's like someone is... is talking to me. Telling me what to do.
Monkian: You better know how that Totem works, Vultureman, or I'll have your gizzard!
Lion-O: Just believe in yourself Snarfer. Use the talents you have and you'll always find a way to do your part as a member of the team.
The Totem of Dera would wield its power simply through the person holding onto it. For some reason Vultureman attached it to a gun, but every indication is that he could simply have held onto it and used it, as both Snarfer and Mumm-Ra did when they used it.