Major Story Arcs
Fenris was invited by the Gamesmaster to join in the Younghunt (in the arc called " Child's Play") in order to motivate the Upstarts. They were immediately successful in capturing Magma. They were thwarted by Moonstar and her psionic arrows, however, when they tried to follow Empath into the Nova Roma encampment. It is uncertain what happened to them next (whether they were jailed and broke out or whether they simply were left alone on the jungle floor and "came to" later) but their next target in the Younghunt was Rahne Sinclair ( Wolfsbane) of X-Factor. This confrontation is off-panel, but it is known that Fenris failed and was taken into custody by X-Factor.
In the Ultimate Universe The Fenris twins run a corporation. They find Gambit and use him to abduct Rogue. They claim to want to help mutants from a corporate stand point. They offer Rogue the ability to control her powers through a suit that they made. They want her to be a spy for them, with her being able to use her powers to gain peoples memories being very useful. However, when Rogue refuses they attack her saying she never really had a choice. Gambit helps Rogue defeat them. Later the Fenris twins start making Sentinels, but are defeated by the X-Men.