At least the conditions were strong. Per CapFriendly
2019 conditional 2nd round pick*
2020 conditional 1st round pick**
2021 conditional 2nd round pick***
conditional 1st round pick****
Conditions: *2019 2nd round pick is the higher of the two picks the Sharks currently own: Panthers and their own.
**Ottawa receives Sharks 2019 1st round pick if Sharks do not make the playoffs. If Sharks make the playoffs, Ottawa receives Sharks 2020 1st.
***Sens receive Sharks 2021 2nd round pick if Karlsson is re-signed. The selection upgrades to a 2021 1st if Sharks reach the Stanley Cup final in 2019.
****Sens receive a 1st RD pick from the Sharks (no later than 2022) if Karlsson is on an Eastern Conference roster (reserve list) during the 2018-19 season.
So, if Sharks... for some odd reason... are not looking like they'll make the playoffs and decide to sell Karlsson at the deadline (as many have mentioned) then most Eastern Conference teams would be out because if they trade him there it's another 1st pick to Ottawa no later than 2022. I feel like Ottawa, and everyone else involved, already knows he isn't going to extend there and they were at least smart enough to set those little conditional pieces up to maximize on a rental.