Quote Originally Posted by Farecry View Post
Why is this spell considered so good when you lose a turn for it?
Consider a barbarian, the class with the best hit dice (d12) in the game. At level 5, the barbarian will have 12 + (4 x 7) = 40 HP, and let's add a +3 CON bonus for another 15, for a total of 55 hp.

Tomb will, as a reaction, instantly give you temporary HP, 50 hp at level 5, or nearly as much as the total HP of the class with the best HP in the game. That's a huge amount and it will enable you to survive when that dragon wins initiative and breathes on you, when that rogue crits you or that paladin crit smites you etc. Sure, you lose your next turn, but you don't use Tomb for any random hit. You save it for the hit that would have otherwise dropped you to zero. Losing your next turn as a reasonable price to pay as you would have lost your next turn anyway had you dropped to zero, and possibly never had another turn other than a few turns to roll death saves.