Gelf appears in Telepath RPG Chapter 2.
Gelf is a Folk-of-the-Woods trader. He has an extreme distrust of mercenaries, because the Mechanics "cuts down our trees, kills our pets." Gelf has very limited grammar skills (this may simply be a trait of his race).
After the Hero eliminates the Mechanic presence in the Great Forest during the Hero's third mission, Gelf sets up his shop in the Great Forest. Gelf's shop sells things that he scavenged from the Mechanics.
Gelf will offer to sell you two "gaggets" when you first meet him. After buying them from Gelf, talk to Helena, and she will give them to Flint. The first gives Psy Points to Flint, and the second gives him the Fire Breath attack. Afterwards, Gelf will sell you a lamp with the indigo orb in it.
"Oh NO! N-n-n-n-no. Who are you? Not lousy mercenary, yes? They cuts down our trees, kills our pets. [He leans in toward you and sniffs you.] You smells like mercenary. But you not looks like mercenary. Well! Welcome to Gelf shop!"
"Gelf have many great things for sale! You like gaggets?"
"[He growls.] Gaggets! Gaggets! They piece of giants, walk around, smash everything! You want?"
"Good! Gelf have two gaggets from lousy mercenaries. One, a thing, give giants strengh. Four hundreds gold. Two, a thing, they breath fire. Four hundreds gold. You want, yes?"
Gelf doesn't speak your language very well, and it can be, at times, hard to understand him (e.g. "gaggets" means gadgets).