This is all way too complicated to actually run at a table - take the tarrasque double its hp and have it reflect on 4/5/6 let the damage go through on a 1/2/3 and give it vunerability to the special sword problem solved - maybe add +5 to its to hit and +10 damage and give it a range attack that does the same exact damage as the bite call it a howl - simple.
Unless your playing epic levels thats a TPK for 95% of groups out there at l20
This is all way too complicated to actually run at a table - take the tarrasque double its hp and have it reflect on 4/5/6 let the damage go through on a 1/2/3 and give it vunerability to the special sword problem solved - maybe add +5 to its to hit and +10 damage and give it a range attack that does the same exact damage as the bite call it a howl - simple.
Unless your playing epic levels thats a TPK for 95% of groups out there at l20
Only solution you really need: Make it fly.