Is it reasonable to assume the 17 shards listed in the book are not the only existing types?

And if not, has anyone specced out any additional ones?

I have found that staying with the Lesser Shard template and keeping the named shards rare prevents the game from becoming "just use a shard" for each character. It seems to be a big hit with the group as the runes retain a special and treasured property. As for the activations, I think of odd utilities to diversify their problem and puzzle-solving toolbox. Here are some of the one my group has found:

• Stone of Sickness
  • Implement : Add the Enervate modifier once without increase the difficulty of a Curse spell.
  • Activation : One target within short range adds +2 Setback die to their next Resilience check this scene or encounter. Cannot be used on the same target more than once per encounter or scene.
• Shard of Needles
  • Implement : Add the Deadly modifier once without increasing the difficulty of a Attack spell.
  • Activation : May pierce a hole the size of a small nail in a surface of soft leather or weaker within short range (GM's decision).
• Aegis Rune
  • Implement : Add the Additional Target modifier once without increasing the difficulty of a Barrier spell.
  • Activation : One target within engaged range gains either +1 Ranged Defense or +1 Melee Defense until the end of their next turn (users choice).
• Liars Spiral
  • Implement : When using the Utility spell to disguise oneself as someone else they have seen within the last day, add +2 Boost die to the Deception check. Disguise lasts a number minutes equal to 5 times the user's ranks in Lore.
  • Activation : Gain +2 Boost and +1 Setback to your next Deception check

Hope this was helpful.

I actually went through my Runebound and Descent games and recorded them as well. Can see all here. I converted to more D&D but still a reference. https://www.scabard.com/pbs/campaign/235523/folder/244417

18 hours ago, IamGazrok said:

I actually went through my Runebound and Descent games and recorded them as well. Can see all here. I converted to more D&D but still a reference. https://www.scabard.com/pbs/campaign/235523/folder/244417

Noice!

Note, the RoT book also describes legendary "Stars", which seem to be even more powerful runestones (or bigger pieces of Timmoran's original Orb). I've actually done a little on those, but it's marked as "Secret" in my campaign site, to keep it away from the players' eyes. As a lark, I based them on the "Treasures of Rule" from the old cartoon Pirates of Darkwater....including a Compass to help find them. (part of the storyline of the campaign).