Alright, my question is pretty simple: since the Wyrwood doesn't have a constitution score and instead gains 'bonus hit points' based on size (10hp since it is small) does this mean it gains 10 bonus hp per level?
If anyone doesn't know what I"m talking about, here are the rules for construct traits...
A construct possesses the following traits (unless otherwise noted in a creature's entry).
•No Constitution score. Any DCs or other statistics that rely on a Constitution score treat a construct as having a score of 10 (no bonus or penalty).
•Low-light vision.
•Darkvision 60 feet.
•Immunity to all mind-affecting effects (charms, compulsions, morale effects, patterns, and phantasms).
•Immunity to bleed, disease, death effects, necromancy effects, paralysis, poison, sleep effects, and stunning.
•Cannot heal damage on its own, but often can be repaired via exposure to a certain kind of effect (see the creature's description for details) or through the use of the Craft Construct feat. Constructs can also be healed through spells such as make whole. A construct with the fast healing special quality still benefits from that quality.
•Not subject to ability damage, ability drain, fatigue, exhaustion, energy drain, or nonlethal damage.
•Immunity to any effect that requires a Fortitude save (unless the effect also works on objects, or is harmless).
•Not at risk of death from massive damage. Immediately destroyed when reduced to 0 hit points or less.
•A construct cannot be raised or resurrected.
•A construct is hard to destroy, and gains bonus hit points based on size, as shown on the following table.
•Proficient with its natural weapons only, unless generally humanoid in form, in which case proficient with any weapon mentioned in its entry.
•Proficient with no armor.
•Constructs do not breathe, eat, or sleep.
Now, as I stated, a Wyrwood is a 'small' construct so it would gain 10 bonus hp. However, does this mean it would gain 10 bonus hp per level? I only ask becaue in hero lab, the Wyrwood is only gaining a single instance of bonus hp (namely 10 bonus hp at level 1). Part of me believe that it is suppose to gain 10 bonus hp per level, but I can't find any rules that support that.
As always, any help would be appreciated.
The bonus HP are a one off size bonus.
All constructs get these bonus HP (see page 307 of the bestiary)and if you break down their stat blocks it becomes apparent that the bonus is only ever applied once.
Also note:
Hit Points: This is the approximate hit point total for the monster. Note that creatures with particularly high Armor Classes or saving throws, or a number of resistances, might have a lower number. Outsiders and constructs typically have lower hit point totals.
As you can see, Constructs are designed to have lower HP as a trade off for their long list of resistances and immunities.