The 40-card deck you are using already existed before the scythe effect happened. Your "starting Health" is part of "start of game" setup; if Renathal is not in the deck, he cannot buff your starting health. (Technically, the second sentence of his effect should be preceded by "Start of Game:")
Note that the order of these effects is random, so it is possible that Renathal can buff your Health before getting eaten by the scythe. The only card that is exempt from this possibility is C'Thun, the Shattered, which always goes first.
The 40-card deck you are using already existed before the scythe effect happened. Your "starting Health" is part of "start of game" setup; if Renathal is not in the deck, he cannot buff your starting health. (Technically, the second sentence of his effect should be preceded by "Start of Game:")
Note that the order of these effects is random, so it is possible that Renathal can buff your Health before getting eaten by the scythe. The only card that is exempt from this possibility is C'Thun, the Shattered, which always goes first.
"Why, you never expected justice from a company, did you? They have neither a soul to lose nor a body to kick." -- Lady Saba Holland