Update to Drupal 8.0.0 beta 14. For more information, see https://drupal.org/node/2544542

core/modules/block_content/migration_templates/d6_block_content_body_field.yml

@@ -0,0 +1,25 @@
+id: d6_block_content_body_field
+label: Drupal 6 block content body field configuration
+migration_tags:
+  - Drupal 6
+source:
+  # We do an empty source and a proper destination to have an idmap for
+  # migration_dependencies.
+  plugin: md_empty
+  constants:
+    entity_type: block_content
+    bundle: basic
+    name: body
+    label: Body
+    display_summary: false
+process:
+  entity_type: 'constants/entity_type'
+  bundle: 'constants/bundle'
+  field_name: 'constants/name'
+  label: 'constants/label'
+  'settings/display_summary': 'constants/display_summary'
+destination:
+  plugin: entity:field_config
+migration_dependencies:
+  required:
+    - d6_block_content_type

core/modules/block_content/migration_templates/d6_block_content_type.yml

@@ -0,0 +1,16 @@
+id: d6_block_content_type
+label: Drupal 6 block content type
+migration_tags:
+  - Drupal 6
+source:
+  # We do an empty source and a proper destination to have an idmap for
+  # migration_dependencies.
+  plugin: md_empty
+  constants:
+    id: basic
+    label: Basic
+process:
+  id: 'constants/id'
+  label: 'constants/label'
+destination:
+  plugin: entity:block_content_type

core/modules/block_content/migration_templates/d6_custom_block.yml

@@ -0,0 +1,24 @@
+id: d6_custom_block
+label: Drupal 6 custom blocks
+migration_tags:
+  - Drupal 6
+source:
+  plugin: d6_box
+  constants:
+    type: basic
+process:
+  id: bid
+  type: 'constants/type'
+  info: info
+  'body/format':
+    plugin: migration
+    migration: d6_filter_format
+    source: format
+  'body/value': body
+destination:
+  plugin: entity:block_content
+  no_stub: true
+migration_dependencies:
+  required:
+    - d6_filter_format
+    - d6_block_content_body_field