There's nothing in the revised rules for adding "success," but it looks like it might just be a typo. When the game wants you to roll another die, it will use the word die/dice.
The Book contains chess strategies. The explorer who has it can add
one die (maximum eight dice) to Knowledge rolls attempted while
playing chess against Death.
I can't find the term "extra success" in the revised rulebook, so here's the errata.
The Bear adds 2 successes to its Might attack roll when it initiates
an attack (not when it's being attacked). The Crocodile adds 1 success
to its Might attack roll when it initiates an attack (not when it's
And always remember the golden rule.
What If There Isn’t a Rule for That? Many hours went into playtesting
this game, but it’s still possible you’ll run into situations where
the game rules or haunt books don’t clearly answer a question about
game play. Don’t let that slow you down. In such cases, come to an
agreement as a group for what makes the most sense and go with it. (If
that doesn’t work, fl ip a coin to decide.) Then continue your
experience in the house.