Cornered racial ability triggers an alchemically unstable mutagenic form. He doesn't know how, why, or even fully what happens, but animals instinctively dislike him and being crowded in makes him extremely nervous.
AC 20 (+2 armor, +7 Dex, +1 size)[+2 dodge vs Animals, +2 mage armor, +4 shield spell, +3 Shield of Faith]
Touch 18 Flat 13
Fort 10 Ref 13 Wil 11 [Evasion, +6 vs Disease]
Movement: 20ft land, 10ft burrow, fits through openings as a tiny creature, 240ft per day Shadow Step
Bombs: +14 touch (4d6+10 or [immolation] 1d6+10 for 4 rounds or [Plague bomb] contagion) DC 24, precise, avoid up to 10 splashed squares