How do you milk Keller for artifacts, anyway?
There are several methods...
Wait until Keller appears in the certain part of the galaxy. And when he leans out of his hole you jupm into the hole. There you meet no Keller, but earn one art.
Then you lean out of the hole, while Keller jumps into it. Thus you do not suffer his weaponry in space and get the 1-st art. Then you can earn another art, struggling Keller in the hole. There are two variants of behaviour:
1 variant. After Keller's hyperspace extermination you get another art. Aterwards there's a dialogue, in which you should choose the words that do not lead to Keller's fly to Klissans. Then you break the wall and fly away to space.
2 variant. Before Keller's hyperspace extermination you should break the wall and patrole that zone. As soon as you finish Keller and he starts his disintegration movements you immediately escape through the "official exit"
Thus you will have no dialogue but an additional art.
BUT: only the
second variant is needed when you jump into the first hole simultaniously with Keller. Thus you can get two arts only if you use the second variant during the first jump, and any of the variants during the second jump.