I'm sure I've suggested this before, but I'll suggest it again - please add the ability to filter by upgrade level. Have five filters

• Not upgraded - show ONLY artifacts which have not been upgraded *at all*
• Level 4 / 8 / 12 / 16 - show artifacts between the selected level and the previous one. IE, if you check "Level 4", you'll see all artifacts with between levels 1-4. If you select "Level" 8", you'll see those between levels 5-8. If you select both, you'll see all artifacts between levels 1-8.