This kind of corner situation occurred in of one of my games at the London Open Go Congress 2004 (although the outside shape has been simplified quite a lot here..) The status of the groups is, to say the least, non-trivial. I just analyzed it for quite some time, hope I got it right. As usual, if you find an error, please add a comment. (Thanks to tenbatsu, lok and tankero for doing so)
(;AW[aq]AW[bp]AW[cq]AW[cr]AW[br]AB[dr]AB[eq]AB[ep]AW[fp]AW[fq]AW[fr]AW[go]AB[ao]AB[bo]AW[bn]AW[bm]AB[cp]AB[dp]AB[cn]AB[eo]AB[em]AB[fm]AW[gk]AW[fk]AW[ho]AW[hl]AW[hm]C[Can black do anything in this corner? Play at T if you think black is unconditionally dead.]LB[hq:T]AB[dn]AW[dm]AW[dk]AW[dl]AW[bl]AP[goproblems]
(;B[ap]
(;W[ds]
(;B[ar];W[bq]
(;B[es];W[cs]
(;B[er];W[as])
(;B[as];W[er]))
(;B[cs];W[es])
(;B[bs];W[cs]))
(;B[bs];W[es]
(;B[ar];W[bq])
(;B[bq];W[ar];B[cs];W[as];B[cs];W[bs];B[dq];W[cs]))
(;B[es];W[er]
(;B[cs];W[dq]
(;B[ar];W[as];B[bq]C[two-stage ko for life.RIGHT])
(;B[bq];W[ar];B[bs];W[bp]C[double ko, black dies.])
(;B[bs];W[ar];B[bq];W[ds]C[double ko, black dies.])
(;B[ds];W[ar]))
(;B[dq];W[cs]
(;B[ar];W[as];B[bq]C[two-stage ko for life.RIGHT])
(;B[bq];W[ar]))
(;B[ar];W[as]
(;B[cs];W[dq];B[bq]C[two-stage ko for life.RIGHT])
(;B[dq];W[cs];B[bq]C[two-stage ko for lifeRIGHT])
(;B[bq]C[two-stage ko for life.RIGHT]))
(;B[bq];W[ar];B[cs];W[dq];B[bs];W[bp]C[double ko, black dies.]))
(;B[cs];W[es]
(;B[ar]
(;W[as];B[bq];W[ar];B[dq];W[bp])
(;W[bq]))
(;B[bq];W[ar];B[bs];W[as];B[cs];W[bs];B[dq];W[cs]))
(;B[bq];W[ar]
(;B[es];W[er];B[cs];W[dq])
(;B[cs];W[es];B[bs];W[as];B[cs];W[bs];B[dq];W[cs]))
(;B[dq];W[es]))
(;W[er]C[This path is for reference only, most of the variations are missing.];B[dq];W[ds];B[ar]
(;W[as];B[bq]C[two-stage ko for life.RIGHT])
(;W[bq];B[bs];W[as]C[direct ko for life, bad for white.RIGHT])
(;W[cs];B[bq]C[black lives, bad for white.RIGHT])))
(;B[cs];W[bs]
(;B[ap];W[ds]
(;B[es];W[er]
(;B[cs];W[fs])
(;B[bq];W[ar];B[cs];W[fs])
(;B[ar];W[bq]
(;B[cs];W[fs])
(;B[dq];W[fs])))
(;B[er];W[es]
(;B[ar];W[bq])
(;B[bq];W[ar]))
(;B[ar];W[bq];B[es];W[er]
(;B[cs];W[fs])
(;B[dq];W[fs]))
(;B[bq];W[ar];B[es];W[er];B[cs];W[fs]))
(;B[ds];W[ap])
(;B[ar];W[ds]
(;B[es];W[er]
(;B[cs];W[fs];B[ap];W[bq])
(;B[dq];W[fs]))
(;B[ap];W[bq];B[es];W[er]
(;B[cs];W[fs])
(;B[dq];W[fs]))))
(;B[ar];W[cs]
(;B[ap];W[bq]
(;B[as];W[ds])
(;B[ds];W[as])
(;B[er];W[as]))
(;B[as];W[ds])
(;B[ds];W[as]))
(;B[ds];W[ap])
(;B[er];W[ap])
(;B[bs];W[cs]
(;B[ap];W[bq]
(;B[ds];W[as])
(;B[as];W[ds])
(;B[er];W[as]))
(;B[ds];W[ap])
(;B[er];W[ap]))
(;B[dq];W[ap])
(;B[as];W[ap])
(;B[fn];W[co])
(;B[co];W[ap])
(;B[hq]C[No, there is a slight sparkle of hope..])
(;B[fo];W[co]))