Among many CIS derbys like Na'Vi - Virtus.Pro and Vega - Empire, Vega - Spirit are not standing separate, but still have a history.
Spirit is not an old organization but has quite some financial support and decent abilities to be a home for decent rosters. First of them immediately brought them to tier-1 level. After signing CIS Rejects with legendary Goblak and RAMZES666 Spirit finally got a team that would qualify to several good LAN tournaments even without further success. By the way, inbefore Shanghai Major Spirit were bootcamping in Vega Squadron teamhouse.
Back in the days Vega were stopped by "dragons" on their way to Shanghai and MarsTV Dota 2 League. But unfortunately that Spirit roster got torn apart from inside. Afterlife and RAMZES left the team and results got much, much worse.
Later Vega and Spirit faced each other quite often, but "dragons" were not able to keep up with the renewed Vega. Yes, on WePlay and DreamLeague teams exchanged blows, but on StarLadder i-League Invitational "sharks" beat their opponent with a devastating 3-0 score. Then "dragons" lost 0-2 on Manila Major and ESL One Frankfurt and haven't met up until Spirit's roster change.
It happened after Boston Major and it featured players that were in Vega but didn't really get along with the others and had to try themselves somewhere else. Iceberg and Fng looked solid in "sharks", but still had to go.
And their revanchist mood got paid off. On DAC qualifiers "dragons" lost their first map showing no resistance but made an incredible comeback and won the bo3 series. On Kiev Major Spirit took the bo1 match as well. Then, on Overpower Cup they were stronger with a 2:1 score once again. So, the following match will be important for both teams. The victory on the event is on stake, even though it's using online format, it still featured strong participants. In case of Spirit victory their confidence will grow stronger, Vega's success will mean that they're still in business.