Toa Tahu? Might need to link through Takua, and through Lego Studios Backlot, using the prototype version of Takua known as "george".
Toa Tahu has a Chronos Number of 5, assuming you accept the caveat about George in Lego Studios Backlot (2001, Adobe Shockwave, dev. Templar Studios) which @ryunumber previously discussed.
Also I'm going to count Minecraft Marketplace content as all being part of one 'Minecraft: Bedrock Edition' game, even though some Mash-Up Worlds have enough changed gameplay to count as their own games. Since you can still play Survival Minecraft as Shadow with a friend playing as Cleopatra.
Note: I couldn't find the skin pack containing Cleopatra, but Ryu Number uses it as a connection pretty frequently so I'm assuming I just don't know Bedrock edition enough to identify it.
Deathstuck is one of the RPG Maker games in the SBARG universe, featuring a character going through a tower containing dead versions of themself from different timelines. And Shadow the Hedgehog is there as an imaginary friend kinda thing. It's normally hosted on rpgmaker.net, but as that site is down, a MEGA mirror can be found here.
