On p115 of the PHB under Arcane Ward there are a few facts that I think are clear:
- The ward is created by the first abjuration spell you cast in a day
- It has a max hp of level × 2 + int modifier.
- The ward does not absorb damage once it reaches 0 hp, but it remains until you take a long rest
- The ward can be recharged by casting abjuration spells, at a rate of 2 x spell level worth of hp 3.
However, the way they wrote the paragraph about recharging seems unclear to me. Can you recharge the ward whenever it is below max hp or only when it is at 0? My understanding of temporary hp would say it is the latter, but the writing on this ability infers the former.
If I were a level 10 abjurer with 20 int and cast Mage Armor, it would give the ward 25 hp. If I took 30 damage from an enemy, the ward would absorb 25 damage, leaving it at 0, and I would take the remaining 5 damage. If I cast Stoneskin (level 4 abjuration) the ward would be recharged with 8 hp. If I then cast Planar Binding (level 5 abjuration) which would be correct?
- The ward remain at 8 hp
- The ward would recharge an additional 10 hp to a total of 18 hp