Create a block with Context to be used in panels and load context entity:node

block_context.php

<?php

namespace Drupal\dies_event\Plugin\Block;

use Drupal\Core\Block\BlockBase;

/**
 * @file
 * Article Library Menu.
 */

/**
 * Provides a 'EventDetailBlock' block.
 *
 * @Block(
 *  id = "dies_event_detail_block",
 *  admin_label = @Translation("Event detail block"),
 *  context = {
 *    "node" = @ContextDefinition("entity:node", label = @Translation("Node"))
 *  }
 * )
 */
class EventDetailBlock extends BlockBase {

  /**
   * {@inheritdoc}
   */
  public function build() {
    $build = [];

    $node = $this->getContextValue('node');
    // Only available on event nodes.
    if ($node->getType() === 'event') {
      $build['dies_event_detail'] = [
        '#theme' => 'dies_event_detail',
        '#node' => $node,
      ];
    }

    return $build;
  }

}